A recording medium detection method uses transmission and reflection photosensors to correctly detect if a recording medium having labels affixed to a liner is in the transportation path. The label printer 1 has a reflection photosensor 26 and a transmission photosensor 27 disposed to the transportation path at positions separated the distance L0 between the labels 12c. Labels 12c on the recording medium 12a can always be detected by either or both the reflection photosensor 26 and the transmission photosensor 27. Because the reflection photosensor 26 is downstream from the transmission photosensor 27, a situation in which a black mark 12d is at the detection position of the reflection photosensor 26 and reflection is not detected and only the liner 12b is at the detection position of the transmission photosensor 27 and transmission of the detection beam is detected is avoided. Detecting transmission without detecting reflection of the detection beam therefore only occurs when the recording medium 12a is not in the transportation path A.