A height adjustment mechanism of a table saw is provided with a support including a concave seat, two first sleeves spaced from both ends of the seat respectively, a guiding hole, and two parallel brackets spaced from the guiding hole; a drive rod rotatably extended through the brackets; a first bevel gear mounted to an open end of the drive rod; first and second guide uprights fastened in the first sleeves respectively; a threaded guide rod inserted through the guiding hole; a second bevel gear at a bottom end of the guide rod to mesh with the first bevel gear; a motor including a threaded guide hole secured to the guide rod, two second sleeves with the first and second guide uprights sliding through respectively; and two support elements each including a concave base member, a sliding rail on the base member, and a fastening member.