To provide a break detector for print ribbon which can detect break very accurately even in the case of a very thin print ribbon.

The break detector for print ribbon comprises a sensor 11 for detecting the rotational speed of a motor 2 winding a print ribbon 1, and a section for making a decision whether the print ribbon 1 has a break or not based on a detected rotational speed. The sensor 1 comprises a rotary encoder interlocked with the winding motor 2 and can detect the rotational speed by counting the number of revolutions per a predetermined time of the motor. The deciding section determines, at first, that the winding motor 2 is rotating and then determines whether the sensor 11 has detected a low speed rotation (normal rotation at the time of printing) of the winding motor 2 or an abnormal high rotation. A decision is made that the print ribbon 1 is not broken if the low speed rotation has been detected otherwise a decision is made that the print ribbon 1 is broken.