A printing apparatus including a platen unit including a platen surface on which a medium is disposed; a carriage including a print head and a sonic sensor, the carriage being configured to move; and a flat surface unit including a plurality of flat surfaces disposed such that distances between the sonic sensor and the plurality of flat surfaces are different from each other. The printing apparatus derives a relational expression from a surface-by-surface distance difference among the flat surfaces of the flat surface unit and a transmission/reception time to and from each surface, obtained based on a measurement by the sonic sensor, and determines, from the relational expression and the transmission/reception time measured at the medium, a distance to the medium.