An image forming apparatus and a lock mechanism including a toggle mechanism capable of eliminating the problem of abnormal noise before and after a lock member passes a neutral point are provided. A lock mechanism includes a toggle spring that rotationally biases a toggle lever toward a standby position when the lever is between a standby position and a neutral point, and implements switching in a direction of the rotational biasing toward a locking position after the lever passes the neutral point. A projection and a locked portion of an engagement member are sandwiched by a toggle base and the toggle lever to maintain a contact state before and after the toggle lever passes the neutral point.