To obtain a mechanism which inhibits the floating of a printing medium at low cost in a dot impact printer.

The dot impact printer is equipped with a ribbon cassette 46 for feeding an ink ribbon 80 between the head end 76 of a printing head 44 and the printing medium 30. Mask holding parts 104, 106 for incurvating and holding a ribbon mask 88 are attached to guide arm parts 84, 86 of the ribbon cassette 46. The curved part 140 of the ribbon mask 88 projects to the side of a platen 32 from the head end 76 of the printing head 44 and be made contact to the printing medium 30 at printing. At that time, an elastic deformation is applied to the printing medium toward the pressed direction, and the printing medium 30 is pressed to the platen 32 by the restoration force of the elastic deformation. Thereby, it can be inhibited that the printing medium 30 floats from the platen 32, and then a noise at printing can be reduced.