A printing device includes a print head configured to execute printing on one surface of a long-size medium to be printed, on the other surface of which a plurality of oblique lines of the same angle of obliquity are formed at regular intervals, a conveying section configured to convey the medium to be printed, a sensor configured to detect the oblique lines, and a control section configured to control the print head to execute printing while changing a position of printing on the medium to be printed in accordance with an interval between the oblique lines in a conveying direction of the medium to be printed detected by the sensor.