An armature which radially faces a magnetic field-producing unit equipped with a magnet unit having a plurality of magnetic poles includes a housing, an armature core, a multi-phase armature winding, and bus bars. The housing includes a cylinder and a disc-shaped end plate placed in contact with one of axially opposed ends of the cylinder. The armature core is disposed on a portion of the cylinder which radially faces the magnet unit. The armature winding is disposed on a portion of the armature core which radially faces the magnet unit. The bus bars electrically connect phase windings of the armature winding together. The armature also includes a bus bar module which is of a circular or C-shape extending along the circumference of the armature core. The bus bar module is secured to the cylinder, the end plate, or one of axially opposed ends of the armature core.