A printer includes an optical sensor configured to image a surface of a medium, and a contact member configured to provide a unique concavo-convex shape by contacting the surface of the conveyed medium on an upstream side thereof. A calculation unit calculates the movement amount of the medium by pattern matching calculation using a correlation window between a plurality of image data acquired at different timings by an optical sensor with the conveyance of the medium. The calculation unit searches in image data first acquired for a unique pattern reflecting the unique concavo-convex shape, and set a region including the unique pattern as a correlation window.