Inexpensive, maintenance-free and high efficiency reluctance motors and generators have a construction that makes it possible to decrease pulsating torque and additional harmonic core loses. Each salient pole of the rotor core of the reluctance motor and generator has a shape such that the gap permeance varies in proportion to cos (N.theta..sub.2), where .theta..sub.2 represents an angular position with respect to the origin set to the center of a salient pole, or a shape analogous to the shape. In order to make up for a reduction of reluctance torque due to the shape, slits are provided inside the rotor core which cause a large reluctance for the quadrature-axis flux without interfering with the direct-axis flux.