Seat device for vehicle

A seat device for a vehicle, comprising:

• a main seat having a main-seat cushion and a main-seat back, the main-seat back projecting upward from a rear end of the main-seat cushion to support a back of a passenger seated in the main seat;
• a sub seat having a sub-seat cushion and a sub-seat back, the sub-seat cushion being connected to the main seat via a support linkage which enables the sub-seat cushion to be stored below the main-seat cushion, the sub-seat back supporting a back of a passenger seated in the sub seat, the sub-seat back comprising a sub-seat back frame and a sub-seat back support member, the sub-seat back support member being configured to connect the sub-seat back frame to the main seat such that the sub-seat back frame of the sub-seat back is at least laterally rotatable relative to the main seat, whereby the sub-seat back is foldable at the main-seat back;
• and
• a seatbelt device for a sub seat, the seatbelt device for a sub seat comprising a retractor to wind up a webbing and a buckle to detachably hold a tongue provided at the webbing,
• wherein said retractor of the seatbelt device for a sub seat is attached to said sub-seat back support member, and said buckle of the seatbelt device for a sub seat is attached to the sub-seat cushion on an opposite side to a disposition side of the main seat in a vehicle width direction.