PURPOSE: To improve the operating properties of a seat and facilitate its one- touch folding, by providing an interlocking member between the back of the seat and a member of its and enabling the forward tilting operation of the back of the seat to automatically unlock the bottom of the seat.

CONSTITUTION: A rear seat 11 comprises a bottom 13, a reclining unit 14 and a back 15. A lockup member 18 is pivotally coupled to the underside of the seat bottom 13. The upper bracket 20 of the reclining unit 14 is provided with a protrusion 20a. An interlocking member 24 is pivotally coupled to the lower bracket 21 of the reclining unit 14. When the seat back 15 is tilted forward, the lockup member 18 is swung through the protrusion 20a of the upper bracket 20 and the interlocking member 24 to unlock the seat bottom 13. The interlocking member 24 may be dispensed with or the interlocking member and the lockup member 18 may be connected to each other by a cable.