A permanent magnet type three-phase stepping motor that is simple in construction,
with vibration, a reduced unbalance force in the radial direction, and high torque
that can be manufactured at a low cost is disclosed. The permanent magnet type
three-phase stepping motor has a stator having 3L pieces of stator pole and a rotor
having a permanent magnet magnetized so as to form a plurality (Nr) of N and S
pole pairs, wherein a condition of 0.3{(Nr/) (Ws+Wr)/(Ds+Dr)}0.5
is established, where L is an integer not less than 1, Nr is L (3n1), n is
an integer not less than 1, Da is an inner diameter of the stator, Dr is an outer
diameter of the rotor, Ws is a width of the stator pole tooth, and Wr is a width
of the rotor tooth.
