To provide a vehicle seat folding mechanism of a simple constitution capable of attaining the towing stroke of an unlocking cable without being affected by the tiltation of a seatback.

A seatback 6 is tilted forwardly, and a first towing member 30 and a second towing member 40 are interlockingly turned by the pressure of an engagement projecting part 20. After towing the unlocking cable 10 connected to the second towing member 40, a projection part 34 is invaded in a groove part 44a of a hole part 42 formed in a concentric shape with respect to a rotary shaft of the first towing member 30. As the first towing member 30 is turned, the projection part 34 is moved along the groove part 44a, and the turn of the second towing member 40 is regulated.