An armature includes an armature coil including a plurality of coil modules and a base member including a cylindrical back core. Each of the coil modules includes a corresponding partial winding of the armature coil and a back-yoke-side insulating wall formed on the back yoke side of the corresponding partial winding. The coil modules are arranged, on a radially inner side or a radially outer side of the base member, in alignment with each other in a circumferential direction. The base member has a plurality of first engaging portions formed therein and each of the coil modules has at least one second engaging portion formed in the back-yoke-side insulating wall thereof. The coil modules are fixed to the base member with each of the first engaging portions of the base member engaging with a corresponding one of the second engaging portions of the coil modules in the circumferential direction.