To provide an ink sheet cartridge in which only a formal ink sheet 21 can be mounted.

Three engaging members 52 are provided projecting from a shaft part 48 having a flange 48a as a spool at the taking up side of an ink sheet 21. By inserting the engaging members 52 into a shaft hole 50 of a side plate 31a of a cartridge main body from the inside so as to be engaged with three fitting holes 53 in a first rotation member 46 having a transmission gear 47 undetachably. An engaging projecting member 66 having a large cross-section on the radium outer side and a small cross-section in the radius inner side is fixed on a predetermined one end of a core pipe 41 on the taking up side such that an engaging part 66a is projected in the inner diameter part of the core pipe 41. In the case where the core pipe 41 is set on the shaft part 48 with an engaging nail 51a at the tip of a bar-like elastic member 51 in a first rotation member 46 facing the inner diameter of the core pipe 41, the engaging nail 51a can be contacted with the side surface of the engaging part 66 so that the rotational force can be transmitted from the transmission gear 47 side to the core pipe 41.