An image processing apparatus which is capable of recovering a normal operation thereof at high speed. A CPU 2001 that controls a printer 108 determines whether or not the printer 108 should be switched from a normal operation mode to a power saving mode. Responsive to input of a signal for causing the apparatus to recover the normal operation mode, the CPU 2001 reads out a power saving mode flag from a flip-flop circuit 11005, and when the flag indicates the apparatus has been switched to the power saving mode, reads out a main program from a SDRAM, whereas when the flag does not, reads out the main from a HDD 2004, for control of the printer 108.