An input/output (I/O) module is configured to connect a controller and a field device. The I/O module includes a PWM (pulse width modulation) demodulator configured to demodulate a PWM signal that is input from the controller, a current source configured to output a current based on an output signal of the PWM demodulator to the field device, a resistance connected in line with the current source, and a feedback circuit configured to feed back an output current of the current source to the PWM demodulator via the controller.