To prevent a malfunction caused by the leakage of light and reflected light from another apparatus by arranging a recording medium detector and a reflection characteristic detector to face each other.

After printing paper 20 is extracted from a paper tray 80, the reflective characteristics of the paper 20 are measured by a measurement part 81. A darkroom box is formed by making a box including a light source and a sensor adhere to the paper 20, and a darkroom box is used also between a paper sensing plate 83 and the paper 20. When the paper 20 is not set in the tray 80, the sensor measures the sensing plate 83. Since the plate 83 is processed to absorb light and absorbs light from the light source without reflecting it, the sensor outputs a low value. In this case, the absence of the paper 20 is recognized by a printer driver. When the output of the sensor is high in value, the specification of the paper 20 from measured data and the change of printing are made possible.