To prevent a broken part from popping outside because of a spring force if a wind shaft is broken when a core is detached, etc., by constituting the core of an outer cylindrical body and an inner cylindrical body, and forming a member to be engaged at an axial central part of an inner circumferential face of the inner cylindrical body and a fitting means to the outer cylindrical body at an outer circumferential face.

A core 40 to which an ink ribbon 12 is wound at an outer circumferential face is constituted of an outer cylindrical body 41 and an inner cylindrical body 43 both formed of synthetic resin or the like. The core is used while the inner cylindrical body 43 is fitted and accommodated in the outer cylindrical body 41. The outer cylindrical body 41 has slits 42 extending at an inner circumferential face in an axial direction via an optional distance. The inner cylindrical body 43 has projecting streaks 45 extending at an inner circumferential face in an axial direction via an optional distance. When an ink ribbon cassette 10 is fitted, engaging hooks of a wind/take-out shaft of a printer can be fitted in recessed grooves 46 between the projecting streaks 45. Moreover, a ring projection 47 as a member to be engaged is provided at an axial central part of the inner circumferential face of the inner cylindrical body 43, and projections 48 to be fitted in the slits 42 of the outer cylindrical body 41 are formed at an outer circumferential face of the inner cylindrical body.