A printing apparatus that is capable of executing, based on printing data, printing onto a first side of a printing medium and printing onto a second side, which is the back side of the first side, after the printing onto the first side is provided. A print density of a predetermined region at a rear end of the printing medium in a transporting direction at a time of printing of the first side is identified based on the printing data. Conversion data, which is a conversion coefficient to make the identified print density equal to or lower than a predetermined density, is acquired. The printing data is converted by means of the conversion data. Printing onto the first side is executed based on the converted printing data.