A device for adjusting a seat of a vehicle is capable of implementing functions including adjusting a position of the seat back and forth, a height of the seat up and down, and tilting or the like by using a plurality of actuators having pistons. The functions of adjusting the position of the seat back and forth, the height of the seat up and down, and tilting or the like are carried out by providing connections between a floor panel and a seat cushion frame through a plurality of actuators and a single link, and selectively moving a piston of each actuator back and forth.