An end surface of a stopper is formed so as to be thick which is substantially the same surface as an outer circumferential surface of a flange portion, and the stopper is engaged with an engaging groove formed at the flange portion, whereby an engaging portion formed at a locking piece of the stopper is elastically deformed and engages with an engaging portion formed at the flange portion. When the stopper is pulled out in the direction away from the surface of the base resisting with elastic force of the engaging portion, an opening portion of a slot can be opened. The paper cutter of the invention enables to take the slider out of a plate in spite of having a simple configuration, and prevent a falling of the slider from the plate even in conveying it.