A stepping motor controller includes: a pulse frequency adjustment circuit that receives a command pulse having a first frequency from an external controller that outputs the command pulse in accordance with an interrupt process performed periodically by the external controller, and generates an alternative command pulse having a second frequency that is lower than the first frequency; and a motor driving circuit that receives the command pulse through the pulse frequency adjustment circuit, and controls a stepping motor to rotate on the basis of the command pulse. The pulse frequency adjustment circuit outputs the alternative command pulse to the motor driving circuit instead of the command pulse received from the external controller, when the first frequency exceeds a predetermined level.