Regarding the relationship among the p pairs of magnet magnetic poles 5, the s coils 7, and the c commutator pieces 9, values of p, s, and c are set such that the following inequalities hold in the present disclosure. That is, a value obtained by dividing the number p of sets (the number of pairs including two as one set) of the magnet magnetic poles 5 by the number s of the coils 7 is set to be larger than 0.5 and smaller than 1. In addition, the number s of the coils 7 is set to be smaller than the number c of the commutator pieces 9.
0.5<p/s<1??(Inequality A)
s<c??(Inequality B)

Note that, “p<s<2p” is obtained if Inequality A is transformed. Therefore, it suffices that the number s of the coils 7 is set to be larger than the number p of sets of the magnet magnetic poles 5 and smaller than the total number 2p of the magnet magnetic poles 5.

FIG. 2 is a perspective view illustrating the rotor 6 including the core 10 from which the electric wire of the coil 7 is removed. Each of the teeth 11 has a column 12 and a blade 13. The column 12 is a portion extending radially outward of the rotor 6. In addition, the blade 13 is a portion having a curved surface shape (an arc surface shape or a shape similar thereto), expanded in the circumferential direction of the rotor 6 from an outer end of the column 12, and is arranged so as to face the magnet magnetic pole 5 in a non-contact manner. The electric wire of the coil 7 is wound around the column 12 in multiple times by a concentrated-winding method.