To provide a seat for a vehicle capable of easily securing safety of a child occupant at the time of mounting a child seat and easily mounting the child seat.

A cushion part 3 of the seat 1 for the vehicle is constituted of a cushion revolving part 5 to make its front edge side, a cushion main part 3a, etc., a support member 6 the front end side of which is axially supported on a car body floor 2 is provided on a lower surface of the cushion revolving part 5, and it is constituted so that a lower part of the child seat 7 is supported by the support member 6 by holding the support member 6 by a holding means in an erected state. Consequently, the child seat 7 is restrained and held by the seat 1 for the vehicle at the time of front collision of the vehicle, etc.