Thirty Meter Telescope (TMT) is a next-generation extremely large telescope with aperture size of 30m under construction by international collaboration involving Japan, U.S., Canada, and India. TMT with Adaptive Optics (AO) will achieve an angular resolution of 0.01 arcseconds and a sensitivity capable of detecting point sources as faint as 30th magnitude. Key sciences of this telescope include exploring the nature of extrasolar planets by direct imaging of Earth-like planets in habitable zones of nearby faint stars, detection of the emission originated from the first massive stars in the universe, and spectroscopic follow-up in multi-messenger astronomy to reveal origins of matter. TMT is a unique extremely large telescope to be constructed in the northern hemisphere, necessary for covering targets in the whole sky with ESO Extremely Large Telescope (E-ELT) and Giant Magellan Telescope (GMT). The optical system of TMT will realize a clean point spread function (PSF), which will be a great advantage over E-ELT and GMT in high-contrast observations for extrasolar planets. High-resolution spectroscopy with high sensitivity is another great advantage of TMT in studying atmospheres of extrasolar planets, precise measurements of radial velocity and redshift variations, and elemental abundances of stars. Toward the completion in the 2030s, Japan is responsible for constructing the telescope structure and the primary mirror segments, as well as developing science instruments. The status of the project will be reported.