To provide a cartridge placement mechanism which ensures the placement stability of a tape cartridge by a simple structure and to provide a tape printing device having it.

The cartridge placement mechanism has a cartridge attaching part 7 to which the tape cartridge 5 is detachably attached to place the tape cartridge 5. The placement mechanism has projecting portions 76 on a surface part (upper surface 71a of a bottom plate 71) provided in the direction the tape cartridge 5. The tape cartridge 5 is placed on an end face portions 76a of the projecting portions. The tape printing device 1 has this cartridge placement mechanism.