PURPOSE: To facilitate handling of a cassette, by enclosing ribbon cassettes for forward printing and backward printing in a common cartridge, discriminating whether the cartridge is one for monocolor printing or one for multicolor printing, detecting the presence or absence of the cartridge, and detecting the presence or absence of the cassettes in the cartridge.

CONSTITUTION: A signal from the first micro-switch 9 is inputted to a controlling circuit 20 through a cartridge-discriminating circuit 16, and a signal from the second micro-switch 14 is inputted to the circuit 20 through a cartridge- detecting circuit 17. Signals from ribbon end sensors 7a, 7b are also inputted to the circuit 20 through a ribbon end detecting circuit 18, and a thermal recording paper fitting signal 19 is also inputted. The fitting conditions of the ribbon cassette are discriminated based on the signals inputted to the controlling circuit 20, and in consideration of the fitting conditions of the cassette, thermal heads 2a, 2b are driven through a head-driving circuit 22 according to a printing command (a), thereby performing printing.