Its success is vitally important to the station project, which is set to lose the servicing capability of the US shuttle fleet next year.
The freighter left Earth atop an H-IIB rocket at 0201 local time on Friday (1701 GMT, Thursday).
The flight to orbit was due to take some 15 minutes.
The HTV mission will be directed by engineers in Tsukuba, Japan, and at the US space agency's (Nasa) mission control in Houston.
It will be commanded to conduct a number of tests of its navigation and rendezvous systems before making a close approach to the ISS.
Docking is not expected to take place until at least day eight of the mission.
The vehicle is carrying 4.5 tonnes of supplies for the space station.
The spacecraft is build by Japan's space agency JAXA, and will lift off on board the country's new H-2B rocket.
The spacecraft is a solar-powered cylinder about 10 meters long and 4.4 meters wide. It can haul up to 6 tons of cargo, but will be loaded with less cargo on its maiden flight.
Report says that the Japanese freighters "will be vital to support the space station's six-person crew once NASA's space shuttle fleet retires in the next year or so."
Unlike the fully-automated cargo ships built by Russia and Europe, which can dock at the station with the use of the Kurs laser-guided docking system, designed and built by Russia's Energia corporation, the HTV-1 will be pulled to the ISS by a robotic arm operated by the ISS crew.
JAXA said it has spent about $680 million since 1997 to develop the HTV spacecraft.
The $220-million vehicle is expected to be "buried" in southern Pacific after spending a month docked with the ISS.

Up and away

Miyake said that H-2B shares many of the same reliable components with H-2A, and so JAXA has confidence in this rocket's maiden flight.
"The launch vehicle is on its first flight, but most components and subsystems are the same as H-2A launch vehicle. The difference is that they have four [solid rocket] boosters rather than the two on H-2A, and two main engine thrusters rather than the one on H-2A."
H-2A has just one failure compared to 14 successful launches on record, and has previously lofted hardware such as Japan's moon orbiter Kaguya. The larger H-2B rocket also requires about 1.7 times more propellant than its smaller predecessor. It stands about 187 feet (57 meters).
The extra carrying capacity allows H-2B to lift almost eight tons to a geostationary transfer orbit. The 16 1/2-ton HTV-1, meanwhile, is destined for a lower orbit to reach the space station, which flies 220 miles (354 km) above Earth.

Free-flyer

Kibo is a giant facility the size of a tour bus that houses experiments in a pressurized interior pod, an attic-like storage room and an external science platform. It has its own robotic arm, two windows and a small airlock.
"It's the first unmanned vehicle that brings with it both pressurized and unpressurized cargo," NASA space station flight director Dana Weigel said in a recent briefing. "It's also the first unmanned vehicle going to the U.S. segment, and the first free-flyer capture from ISS."
A free-flyer capture means that space station astronauts must use a Canadian robotic arm to grab the free-floating HTV-1.
The space freighter does not automatically dock like the European and Russian spacecraft. Instead, a preprogrammed computer controls HTV-1's approach up until the moment of robotic grapple. The robotic arm operator, NASA astronaut Nicole Stott, must then seal the deal within a 99-second capture clock.

Moving to manned spaceflight

No concrete plans exist yet for a Japanese manned space program, even if Japanese astronauts have already flown to the space station and tested odor-free underwear in microgravity. But HTV-1 could provide some of the core technologies for Japanese astronauts to take their own rides into space.
Currently HTV will be disposed of in the atmosphere. But if they could add some return capability to HTV, it could be one of the technologies for manned spaceflight.
Such a development could parallel European proposals to refit their ATV cargo ship for proper reentry, rather than simply burning up in the atmosphere.
This HTV technology will contribute to future moon and Mars missions, and to international cooperation.