LCGT (Large-scale Cryogenic Gravitational wave Telescope) is a laser interferometric gravitational wave detector that is constructing at Kamioka-mine, Japan since 2010. LCGT aims to detect gravitational waves from astronomical objects : binary coalescence of neutron star, black holes, supernovae, etc. LCGT's sensitivity is designed as comparable to other world wide projects advanced LIGO (US) or advanced Virgo (Italy/France). These detectors are insanely great as that only 10^{-24} distortion of space-time will be measured. To achieve these high sensitivity, LCGT site is chosen under mountain for silent and stable environment, and laser mirror will be cooled in cryogenic temperature. We will introduce the fundamental principle of gravitational wave detection, report status of construction of LCGT, and discuss about physics/astrophysics of gravitational waves.