The printer is a printer for printing on a label continuous body including a label detecting unit having a light-emitting portion configured to emit a detecting light and a light-receiving portion configured to receive the detecting light and a control unit configured to adjust a light emitting output of the detecting light in the light-emitting portion, so as to bring an output voltage from the label detecting unit when the light-receiving portion receives a detecting light through the liner to which the label is not temporarily attached, closer to an output voltage from the label detecting unit when the light-receiving portion receives a detecting light through a state in which there is no label continuous body between the light-emitting portion and the light-receiving portion.