There is provided with an image communication apparatus. A serial interface transfers data between a master and a slave. The master supplies a clock signal to the slave. An oscillation generator generates a clock signal. A switch selects, and supplies to the slave, either the clock signal output from the oscillation generator or the clock signal from the master. A controller stops an operation of the master and controls the switch such that the clock signal output from the oscillation generator is supplied to the slave, upon transition to a power saving mode.