To provide a vehicle seat with a flip-up seat locking mechanism configured to lock a seat cushion in a tip-up state where the seat cushion is flipped up toward the seat back by simple operation from the outside of a cabin.

A pin member having a retaining flange portion is inserted into a hinge bracket that rotatably supports the seat cushion on the side thereof so as to move in a shaft direction. In a cushion frame of the seat cushion, an engagement hole into which the pin member is inserted is provided at the position facing a tip of the pin member when the seat cushion is in the tip-up state. Alternatively, the engagement hole is provided at the position facing the tip of the pin member of the hinge bracket when the pin member is inserted in the cushion frame. When the pin member is inserted in the engagement hole while the seat cushion is flipped up, a flange portion of the pin member is engaged with an edge of the engagement hole by the weight of the seat cushion, and the seat cushion is locked in the tip-up state.