PURPOSE: To prevent the falling off of a magnetic cylinder from a sleeve at the time of assembling the cylinder in the sleeve by putting a projecting section provided on a sliding member or sliding pipe in an annular groove formed on a shaftless columnar magnet.

CONSTITUTION: A sleeve 2 fitted with a sleeve supporting means 6 at one end is manufactured. A shaftless columnar magnet 1 and the sleeve 2 are supported so that they can rotate against each other by putting an opened-end side sliding member 4 with a projecting section 4b in the annular groove 3 of the magnet 1 and putting a sliding pipe 5 on the magnet 1 on a sleeve supporting member side. The internal surface of the member 4 is formed in a smooth sliding surface and the sleeve 2 and member 3 integrally rotate against the magnet 1. On the other hand, the internal surface of a pipe-like section 5a on the sleeve supporting mean side is formed in a sliding surface and the sleeve 2 and pipe 5 integrally rotate against the magnet 1. The separating distance between the surface of the magnet 1 and the internal surface of the sleeve 2 can be reduced when the molded thicknesses of the member 4 and the section 3a of the pipe 5 are reduced.