PURPOSE: To indicate a sheet size in a simple and reliable manner by detecting and indicating the sheet size through the contact between a magnetic board and a reed switch installed on a sheet cassette and a copying machine main body stopper, respectively, when the cassette is held at a specified position by the stopper.

CONSTITUTION: When the size of a sheet of paper to be contained in a cassette 8 is A-4, for example, a magnetic board 12 is inserted into one of a pair of through holes 10a provided at the end surface of the cassette 8, which abuts on a stopper 9 of a copying machine main body. With this state maintained, the cassette 8 is pushed in until it abuts on the stopper 9 and is kept as it is attached to the copying machine main body. Then, a reed switch 13a, which abuts on the magnetic board 12, closes to light a lamp 15a, while indication "A4" on a plastic board 16a is clearly illuminated. On the other hand, when the size of a sheet of paper to be contained in the cassette 8 is "B5", the magnetic board 12 is inserted into the other through hole 10b.