An electromagnetic coil is fixed in a rotor through an insulation member. A slip-ring rotating with a rotor and a brush supplying electric current to the slip-ring are disposed radially inside a boss portion of a compressor housing. The slip ring is attached to the rotor through a slip-ring supporter, and the brush is supported by the boss portion through a brush supporter. The brush supporter includes a cylindrical sleeve radially inside the brush, which extends axially outwardly farther than a slide surface between the slip-ring and the brush.