A sheet supplying unit having no need to place a great many skew sensors and enabling printing apparatus to simplify structure and to reduce cost. The sheet supplying unit moves a skew sensor to a most left sensor position in which the table sensor detected that the print medium exists, detects the upper edge of print medium, and executes a skew detection; in the case that the print medium is narrow, moves a skew sensor, detects the upper edge of print medium, and executes a skew detection; in the case that a position of skew sensor does not place at a position keeping a predetermined margin at the inside of the print medium, moves skew sensor to the inside of the print medium and executes again an inclination detection; or according to print medium width and skew sensor width, changes a skew judgment quantity.