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 has a reflection photosensor and a transmission photosensor disposed to the transportation path at positions separated the distance between the labels. Labels on the recording medium can always be detected by either or both the reflection photosensor and the transmission photosensor. Because the reflection photosensor is downstream from the transmission photosensor, a situation in which a black mark is at the detection position of the reflection photosensor and reflection is not detected and only the liner is at the detection position of the transmission photosensor 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 is not in the transportation path.