A printer includes a top plate, a stabilizer bar, a screw, and a positioning member. The top plate is adapted for a piece of paper located thereon and defines a locking hole. The stabilizer bar is slidably attached to the top plate and defines a through hole and a step-shaped hole. The screw is screwed into the locking hole from the through hole. The positioning member includes a threaded portion. The threaded portion is mounted in the step-shaped hole. A part of the threaded portion extends out of the step-shaped hole, and the part of the threaded portion abuts the top plate.