A printing apparatus and a print position aligning method are provided which can execute a dot position adjust value calculation mode normally and smoothly without requiring the user to make decisions or adjustments. A test pattern to check the width of a print medium is printed and is detected by an optical sensor to decide whether or not a dot position adjustment pattern can be printed. Before the dot position adjustment pattern is printed, a decision is made as to whether the print medium supplied is appropriate or not. If the print medium supplied is smaller than a size specified for the dot position adjust value calculation processing, the print medium is discharged without being printed with the dot position adjustment pattern. This eliminates a possibility of a wasteful consumption of print mediums and of contaminating the interior of the printing apparatus.