An image forming apparatus which eliminates a need for a user to operate a mobile terminal each time he or she sends an image file from the image forming apparatus using a cloud service and therefore enhances ease of operation. First user authentication of the user is performed for the image forming apparatus. Image data read from a scanner is converted to an image file, which in turn is sent to a destination set on a transmission destination setting screen. Based on the authenticated user, an access token to be used is selected from at least one access token managed in a hard disk of the image forming apparatus so as to use a function of an external server. Second user authentication for the external server is performed using the selected access token. After that, the image file is sent using the function of the external server.