To provide an ink ribbon cassette and a printer capable of performing clear print constantly on a medium.

The printer 1 comprises an ink ribbon cassette 12 having an accumulated number of printed characters storage section 14 for storing the number of characters printed using a currently incorporated ink ribbon, a specified number of printed characters storage section 6 for storing the number of characters printed before the ink ribbon reaches a replacement time as a specified number of printed characters, a counter 3 of the number of printed characters for calculating the accumulated number of printed characters by adding the number of printed characters to those stored in the accumulated number of printed characters storage section 14 every time when printing is performed, and a lifetime judging means 7 for storing the accumulated number of printed characters calculated by the counter 3 of the number of printed characters in the accumulated number of printed characters storage section 14, comparing the accumulated number of printed characters with the specified number of printed characters stored in the specified number of printed characters storage section 6, and judging that the replacement time of ink ribbon has reached if the accumulated number of printed characters is more than the specified number of printed characters.