An image forming apparatus is provided with a processing unit that performs a predetermined process, a power-supply shutting unit that shuts off power supply to the processing unit when a predetermined door is opened, a voltage detecting unit that detects a decrease in voltage at a point located posterior to the power-supply shutting unit, and a communication control unit that does not initiate communication with the processing unit if the decrease in voltage is detected by the voltage detecting unit before a start of the communication with the processing unit, and judges the just-ended communication as abnormal if the decrease in voltage is detected by the voltage detecting unit after the end of the communication with the processing unit.