An image formation device (100) comprises a unit (30) that can be attached to and detached from a body frame (101), and a lock mechanism (40). The lock mechanism (40) has a grip part (37) that can move reciprocally in the attachment direction and the detachment direction of the unit (30), a lock member (41) that is swingably positioned in the unit (30) and has a hook part (41b) capable of engaging with an engagement-receiving part (50) formed on the body frame (101), and a first biasing member (43) that biases the lock member (41) in a first direction, in which the hook part (41b) engages with the engagement-receiving part (50). Due to the grip part (37) being moved in the detachment direction, the lock member (41) swings in a second direction that is the opposite of the first direction, in opposition to the biasing force of the first biasing member (43), and the engagement of the hook part (41) and the engagement-receiving part (50) is released. The lock member (41) has a restriction part (41e) that restricts the swinging of the lock member (41) in the second direction while the grip part (37) is not moved in the detachment direction.

An image forming apparatus includes an apparatus main body having a receiving portion on a conveying path, an open/close unit movable between open and close positions, a roller located on the conveying path when the open/close unit is closed, a pressure applying unit applying pressure to the roller, and a separation unit movable between first and second positions. When at the first position, the roller contacts the receiving portion with pressure from the pressure applying unit. When at the second position, the roller is separated from the receiving portion. A switching device switches the separation unit's position, controlled by a control unit. An open/close detecting unit detects the open/close unit's state. If the separation unit is at the second position and the open/close unit is detected at the open position, the control unit controls the switching device to move the separation unit to the first position.