A printing apparatus includes a transport unit configured to transport a printing medium, a platen that includes a first support surface supporting the printing medium, a light-emitting unit configured to emit detection light toward a transport path of the printing medium, and a light-receiving unit provided adjacently to the light-emitting unit and configured to detect reflected light of the detection light, wherein a recessed portion is provided in the platen, the recessed portion including a primary reflection surface receiving the detection light and a secondary reflection surface receiving the detection light reflected by the primary reflection surface, and the first support surface and the secondary reflection surface overlap in an optical axis direction of the detection light.