PURPOSE: To simplify manipulation by supplying paper feed information similar to that for the time of installing a cassette to detecting means mounted on a main body unit for detecting the existence of paper stored in a cassette.

CONSTITUTION: An upper cassette 101 and a lower cassette 102 are inserted in a main body unit 103 of a printer or the like, and the existence of the cassettes is detected by switches 104, 105, respectively. The existence of paper in each cassette is detected by respective pairs of lamps 106, 108 and photo sensors 107, 109. The lower cassette 102 selected by the main body unit 103 and properly insetalled will be detected by the switch 105 for detecting the existence of a cassette. Paper 110 intercepts light emitted from a light source 108 to the photo sensor 109, thereby indicating that paper is existent, so that the printer is in the operable state. Thus, the cassette can be mounted and demounted without any change of paper detecting means of the main body unit.