To rotate a motor smoothly by suppressing the fluctuation of a rotary speed caused by the fluctuation of a load torque during on rotation, in a method of controlling the motor.

When the speed of a motor is a target one, one rotation of the motor is equally divided into a plurality of sections in terms of a mechanical angle, the time required for one rotation is measured based on the position detection signal of the motor. At the same time, the time required for one rotation is divided by a division number to calculate section average time T, and time for each of a plurality of sections (section time (t)) is measured (step ST1). The section average time T is compared with the section time (t) (step ST2). In a section, where the section time (t) is smaller that the section average time T, a correction amount α is subtracted from the correction value of the application voltage of the motor for updating (step ST3), while in a section where the section time (t) is larger than the section average time T, the correction value of the application voltage is increased by the correction amount αfor updating (step ST4), thus bringing the rotary speed of each section closer to the average value.