The IRTS is a first Japanese infrared satellite mission which will be launched on February of 1995 by HII rocket. The IRTS is one of the mission experiments aboard the small space platform, SFU. The telescope aperture of the IRTS is 15cm, but is cooled by liquid Helium to realize very low background condition. Four instruments are installed on the focal plane which cover wide wavelengths from near infrared to submillimeter regions. The IRTS is optimized to observe the diffuse extended emission, and will survey about 10% of the sky in 20 days of mission life. The IRTS will provide significant information on cosmology, interstellar matter, late type stars, and interplanetary dust.