PURPOSE: To simply and certainly mount an adaptor on a mounting stand, in an ink ribbon cassette adaptor for mounting an ink ribbon cassette on the mounting stand of a printer, by providing a mounting and fixing self-adhesive part to the rear surface of the adaptor.

CONSTITUTION: In an ink ribbon cassete 1, a rotary receiving part is arranged to the rear surface of the housing 8 having, for example, a circulated and transferred endless ink ribbon 2 received therein. A plurality of holding parts 15, 16 holding the cassette 1 in a detachable manner and the opening part 12 corresponding to the rotary receiving part are formed to an ink ribbon cassette adaptor 11. Further, the engaging part 6 and receiving groove 7 respectively engaged with the holding parts 15, 16 are formed to the cassette 1. In this case, a plurality of mounting self-adhesive tapes 13, 14 are provided to the rear surface of the adaptor 11 as the self-adhesive parts for mounting the adaptor on the ribbon mounting stand of a printer. The adaptor is simply and certainly mounted on the mounting stand through the tapes 13, 14.