A seat for a vehicle having a fold-and-dive function is proposed. When a seatback is rotated forwards and folded, a seat cushion is moved down, so the fold-and-dive function of the seat is realized. When a full-flat mode is realized by the reclining operation of the seatback, a rear end of the seat cushion is moved up, so a step between the seat cushion and the seatback can be significantly reduced or eliminated. Furthermore, a front link connecting a back cushion interlocking frame and a cushion fixing bracket to perform the fold-and-dive function is installed to have directivity where it is inclined rearwards, thus preventing a submarine phenomenon of the seat in the event of a forward collision.