Seat with locking device

A seat portion (2) has seat surface (3) supported by floor surface (4) in region of front seat side (5). A backrest (7) is pivotally connected to seat portion by a pivot axis (9). The backrest is arranged at lower end of seat surface so that a support end (12a) of backrest is extended to floor surface. A support (7a) supports the seat in seat back portion (14) relative to floor surface. A cam track device (11) is provided in support end of backrest for sliding the support along a curve track at time of pivotal movement of backrest relative to seat portion in seat reverse direction.