An output module of an industrial control apparatus includes an output circuit controlling an electrical connection between a power supply terminal and an output terminal and a controller controlling an operation of the output circuit. The output circuit includes multiple switches, which are connected in series between the power supply terminal and the output terminal, and a voltage divider circuit outputting a divided voltage. The controller controls on/off states of the switches, and detects a short circuit of the switches based on the divided voltage. When the divided voltage detected during an off period while the multiple switches are in off states is within a normal voltage range, the controller determines that no short circuit is occurred. When the divided voltage detected during the off period is out of the normal voltage range, the controller determines that a short circuit is occurred in at least one of the switches.