An image processing apparatus capable of preventing erroneous transmission due to a change in destination information in a shared address book. A CPU acquires destination information including at least an identifier and a destination, and a destination of the image data is designated from the acquired destination information. Information on the designated destination of the image data is stored in a destination usage history table. The CPU determines whether or not the acquired destination information has been changed by comparing the designated destination information and the destination information stored in the destination usage history table. If it is determined that the destination information has been changed, a screen for confirming the destination information is displayed. The destination information is designated from the acquired destination information according to a user's confirming operation on the displayed screen.