The present invention relates to an interface circuit of a motor driving apparatus, the interface circuit comprising a power circuit unit for controlling driving of a motor, and a control panel unit which controls the power circuit unit and provides a user interface, wherein the power circuit unit further comprises a second MCU which controls a relay and an additional device unit and detects an operation state of the additional device unit, and the second MCU can communicate with a first MCU of the control panel unit via a communication line.