A motor control circuit controls an operation of a motor based on an input voltage and a control parameter. A voltage-abnormality detection unit detects abnormality of the input voltage by comparing the input voltage with an allowable voltage range. A memory stores therein a plurality of allowable voltage range candidates made to correspond to a plurality of reference voltages and a plurality of control parameter candidates made to correspond to the plurality of reference voltages. A reference-voltage acquisition unit acquires reference voltage information specifying one of the plurality of reference voltages. A selector selects one of the plurality of allowable voltage range candidates from the plurality of allowable voltage range candidates, corresponding to the one reference voltage, as the allowable voltage range and one of the plurality of control parameter candidates from the plurality of control parameter candidates, corresponding to the one reference voltage, as the control parameter based on the reference voltage information.