Short pulses of quasi-monochromatic X-ray in 10–40 keV have been generated via the laser Compton scattering (LCS) of an ultra-short laser pulse with a high density electron pulse. The LCS hard X-ray source consists of a compact S-band 40 MeV linac and a Ti:sapphire laser system. It has been developed at AIST in order to be applied to medical uses. The refraction contrast imaging of a biological specimen has been successfully demonstrated with the LCS hard X-ray. The LCS X-ray source will be a powerful tool for advanced medical diagnosis.