A permanent-
magnet rotating
machine includes a rotor having a rotor core carrying on its curved outer surface multiple permanent magnets arranged in two rows along an axial direction in such a manner that the permanent magnets in one row are skewed from those in the other row in a circumferential direction by a row-to-row
skew angle (electrical angle) thetae, and a
stator having a cylindrical
stator core in which the rotor is disposed, the
stator core being provided with stator coils for producing a
rotating magnetic field for rotating the rotor. A
lower limit of the row-to-row
skew angle thetae is set at a value larger than 30 degrees (electrical angle). A
cogging torque ratio, or the ratio of a
cogging torque occurring in the absence of
skew to a
cogging torque occurring when the permanent magnets are skewed, at a row-to-row
skew angle of 30 degrees is calculated based on the relationship between the cogging torque ratio and the row-to-row
skew angle thetae and B-H curve properties of the stator core, and an upper limit of the row-to-row
skew angle thetae is set at a value not larger than its maximum value at which the cogging torque ratio does not exceed the calculated cogging torque ratio at 30 degrees.