An image processing apparatus includes a first storage area for storing firmware including a processing program for communication processing with an external terminal, and a processor. A processor starts execution of the processing program when a request to start the communication processing is received from the external terminal during execution of the firmware in the first storage area, and stores a modification program supplied into a second storage area when the modification program is received during execution of the processing program. The modification program is a modified program of at least a partial program in the processing program. The processor terminates execution of the processing program when a request to terminate the communication processing is received, and rewrites the processing program in the first storage area using the modification program in the second storage area when execution of the processing program is terminated.