An image processing apparatus capable of properly executing a plurality of processes, method of controlling same, and storage medium

A multifunction peripheral that is capable of performing, in parallel, a plurality of processes including a scanning process on an original using a scanner section. A RAM holds image data generated by the scanner section. A scanner transfer section transfers data from the scanner section to the RAM. A transfer rate of data from the scanner section to the RAM is set by switching at least between a first transfer rate and a second transfer rate lower than the first transfer rate. In a case where a plurality of processes including the scanning process are executed in parallel, a data transfer rate is switched by switching the data transfer rate based on a user's operation performed on a console section.