A magnet type rodless cylinder provided with a slide magnetically coupled with a piston arranged in a cylinder tube and a slide able to move outside of the cylinder tube. The slide has a connection mount detachably attached to it. When attaching the connection mount, the position where the connection mount and an end cap strike/contact becomes the striking/contacting position of the piston. When using a rodless cylinder without a connection mount, the distance between the slide and an end cap when the piston is positioned at the striking/contacting position becomes longer than the striking/contacting distance due to the removal of the connection mount. Therefore, external dampers able to strike/contact the slide are detachably attached to the end caps at the slide sides. Due to this, regardless of the use or nonuse of a connection mount, the piston and slide can always stop at the striking/contacting position.