In a printing apparatus for performing printing on labels of roll paper formed by winding a label sheet with the labels peelably attached to the label sheet, a label remaining number detecting unit, during a printing operation, determines a thickness of the label sheet from a length between the labels included in the label sheet fed out from a label sheet feed-out unit to a printing unit, the length being determined by a label length detecting unit while a distance to a cylindrical outer surface of the roll paper detected by a distance sensor.