A seat apparatus for a vehicle includes a first lock mechanism switching between a first locked state and a first lock-released state and a second lock mechanism switching between a second locked state and a second lock-released state. The first lock mechanism includes a restraining member and a releasing member. The restraining member restrains a pivotal movement of a seatback at a predetermined angle position, at which the seatback does not interfere with a seat cushion moving between a first position and a second position thereof, when the second lock mechanism is in the second lock-released state. The releasing member is linked to the restraining member and releases a restriction to the pivotal movement of the seatback by being moved in association with a movement of the seat cushion when the second lock mechanism is in the second lock-released state.