An image processing apparatus capable of preventing a copy protect function of a video or other contents signal from being disabled. An encoder encodes a contents signal from a DVD reproduction unit. A copy protect circuit performs copy protect processing on the encoded signal and outputs it. The copy protect circuit is controlled by control data input from CPU via an I2C_IF circuit. At this time, verification data from the CPU is stored in, and then read from registers in the I2C_IF circuit. Then, the CPU verifies the destination of transmission of the control data.