An image forming device includes a frame, a subunit detachably attached to the frame, a frame-side positioning portion, a subunit-side positioning portion, the subunit being positioned relative to the frame by making the subunit-side positioning portion contact the frame-side positioning portion, a contact regulating member attached to the frame movably between a location to contact the subunit before the subunit-side positioning portion comes into contact with the frame-side positioning portion in process of the subunit being attached to the frame from a detached state and a location to be kept from contacting the subunit, a pressing member attached to the frame movably between a position to press the subunit such that the subunit-side positioning portion is made contact the frame-side positioning portion and a position to be kept from pressing the subunit, and an interlocking member interlocking movements of the contact regulating member and the pressing member.