An image processing apparatus including: at least one connector including at least one connection pin configured to be connected to an external device; an interface which interfaces transmission of signals to the connection pin through a first wiring formed between the interface and the connection pin; a switching unit which is switched on to transmit a signal through a second wiring which is formed differently from the first wiring to feedback the signal from the connection pin to the interface; a controller which controls the switching unit to allow the feedback of the signal through the second wiring to transmit a preset test signal from the interface to the first wiring at the time of inspecting a signal transmission state of the connection pin and the first wiring, and determines the signal transmission state based on a change of the test signal feedbacked to the interface through the second wiring.