Provided are a seat state switching mechanism which can achieve switching between a walk-in state and a reclining state even with a small number of components, and a seat including the seat state switching mechanism. A seat state switching mechanism is a mechanism which can switch a state of a seatback between a walk-in state and a reclining state, the seat state switching mechanism including: a movable bracket tiltable together with the seatback; a locking member for locking the movable bracket at a predetermined walk-in locking position: and an input member, a first biasing member, and a second biasing member, each composing a releaser, for switching the state of the seatback to the reclining state by releasing a biased state of the locking member in receipt of a reclining operation force.

A lock device is provided with: a latch unit having a slit which allows a striker to enter and exit and configured to engage with and to be disengaged from the striker; and a support member for supporting a spring member outside the latch unit in such a manner that the spring member extends in the width direction of the slit. The spring member is elastically deformed when in contact with the striker having entered the slit, and as a result, the spring member applies pressing force to the striker, the pressing force acting in the direction in which the striker exits the slit.