A seat device for a vehicle capable of easily and certainly holding a seat in a storage position. The outer end in the vehicle width direction of a seat cushion (12) of a seat (10) for the vehicle is supported rotatably about a drive shaft (30) having an axis along the longitudinal direction of a vehicle body. The seat cushion (12) can be switched between a seating posture allowing an occupant to be seated and a storage posture erected along a vehicle room internal side surface (S) by being rotated about the drive shaft (30) by a drive motor (42). The seat (10) for the vehicle taking the storage posture is held in the storage posture by the engagement of a striker (46) with a seat dragger (48), and when it is switched to the seating posture, the striker (46) is disengaged from the seat dragger (48).