1. A printing apparatus for printing an image stored in a mounted storage medium, comprising: an external interface unit configured to connect to an external storage device; a determination unit configured to determine whether or not a second image being a duplicate of a first image is stored in the storage medium and/or an external storage device, in a case where the external storage device is connected to the printing apparatus; printing inhibition unit configured to inhibit printing of the second image determined by said determination unit, in a case of printing images stored in the external storage device and/or the storage medium; an image processing unit configured to read out image data of images to be printed except for the second image inhibited by said printing inhibition unit from the external storage device and/or the storage medium and convert the image data to generate print data; and a first printing unit configured to print in accordance with the print data generated by said image processing unit.