Excitation position is changed in accordance with an external clock. The state of a full bridge circuit including four transistors connected to a coil of a stepping motor, is controlled in accordance with the excitation position. At the time of transition from the excitation position at which coil current that flows in the coil is nonzero to the excitation position at which the coil current is zero, a switch is made to (i) the inverse state where the on or off state of each of the four transistors before the transition is inverted, and then a switch is made to (ii) the off state where all the four transistors are off.