PURPOSE: To obtain a seat lifter having a large strength and safety by carrying- out the vertical adjustment and seat-angle adjustment by installing a supporting point at the front part of a seat cushion.

CONSTITUTION: A turning supporting point 8 is installed at the front part of the cushion frame 9 of a seat, and a link mechanism constituted of an arcuate link 16, etc. is installed at the rear part, and a lock mechanism is installed onto one link mechanism. The lock mechanism is constituted of a toothed disc 23 axially installed onto the cushion frame 9, and an offset pin 25 installed at the position eccentric from a shaft pin 24, and the offset pin 25 is inserted into the long groove 26 of the arcuate link 16. A stopper 28 having projection teeth 29 inserted into the toothed groove 27 of the toothed disc 23 is installed to serve as revolution stopping means.