This invention relates to a printing apparatus and control method thereof. The standard size of an envelope to be stored in each of a plurality of paper storage units configured to store an envelope to be used in printing is set. An offset amount to be used to print an image on an envelope of the set standard size is set. A paper storage unit which stores an envelope to be used in printing is selected from the plurality of paper storage units based on a standard size of an envelope that is designated by a user. The position of an image is shifted in accordance with the set offset amount, and the image is printed on an envelope fed from the selected paper storage unit.