A data processing apparatus that can flexibly deal with various needs of a user while effectively utilizing a memory unit thereof that can store a plurality of data. The data processing apparatus, which is equipped with a memory unit capable of storing data, executes processing of transmitting the data of the memory unit to an external apparatus and erasing the data of the object of transmission to the external apparatus from the memory unit. An acceptance of a specific user request related to processing of the data transmitted to the external apparatus is allowed in a case where the data has been transmitted to the external apparatus. The data processing apparatus executes processing using the data transmitted to the external apparatus in a case where the acceptance of the specific user request is performed via the user interface unit.