Disclosed is an image processing apparatus including a reading unit that reads a document, an image forming and outputting unit that performs an image forming and outputting process, a read image transfer circuit that processes and transfers read image information so as to input the read image information to a controller of the image processing apparatus, an output image transfer circuit that processes and transfers output image information so as to input the output image information to the image forming and outputting unit, and a clock oscillator that generates clocks to be supplied to the read image transfer circuit and the output image transfer circuit, wherein the clock oscillator individually alters clock supply states for supplying the clocks to the read image transfer circuit and to the output image transfer circuit, depending on an operating mode of the image processing apparatus.