PURPOSE: To correctly discriminate the timing of replacing a transfer material by a method wherein the remaining amount of the transfer material to be transferred to a transfer medium is detected by a remaining amount detection means, and the possibility of image forming is discriminated according to the remaining amount and the set number of sheets by a discriminating means.

CONSTITUTION: On a level indication part 44 on an operation panel 14, the remaining amount of an ink ribbon detected by a remaining amount detector 53 is indicated. With the input of the number of sheets to be printed from a ten key 42 on the operation panel 14, the detection output of the remaining amount detector 53 is discriminated. If it is less than the set printing number, a shortage of ink ribbon is indicated on an indication part 45. Then, by resetting the printing number fewer or replacing a ribbon cassette with a new one, the indication part 45 is put out, and a printing possible indication is shown on an indication part 43. By operating a print key 41, a motor drive part 52 and a thermal head 22 are driven to conduct printing on paper P. Therefore, the use-up of ink ribbon during printing can be prevented, and a printing for the set printing number of paper is ensured.