To provide a seat belt installing structure for improving comfortability and boarding-alighting performance, restraining complexity of a frame structure and a weight increase in a seat, and obtaining proper occupant restricting performance.

This vehicular rear seat device has a three-person sitting bench seat 2 having a seat cushion 7, seat belt anchors A, B, C, and D for one side of a central seat part 4, a one side seat part 5, the other side of the central seat part 4, and the other side seat part 6 respectively arranged by two pieces on two central frame materials 23 (30), and 24 (31) of the seat cushion 7, and a seat slide device 3 composed of fixed rails 28 fixed to a car body floor via a leg member 27 and a movable rail 29 slidably installed on these respective fixed rails 28, and fixed to the respective central frame materials. The rails of the seat slide device 3 are arranged near the center of the seat cushion 7.