To sense an ink ribbon remaining amount in a cassette by an inexpensive constitution without providing an optical sensor and an encoder or the like for the sensing of the remaining amount at an ink ribbon taking up roller section in a color image forming device using an ink ribbon cassette.

When the head searching operation of the ink ribbon is performed, by measuring a period of time required for the passing of a marker by a means 5 detecting the printing starting position marker 7 on the ink ribbon 1, or a moving amount of a rotation driving source for the ribbon taking up, the diameter of the taken up ink ribbon which has already been used is calculated, and the ink ribbon remaining amount is estimated. By making the printing starting position marker sensing means work for both purposes, the sensing of the remaining amount becomes possible without separately providing an ink ribbon remaining amount sensing means.