2 b of the case main body 2 is disposed to a back surface side of the thermal head 6 thus a space in the back surface side of the thermal head 6 can be made smaller and a width dimension thereof can be reduced which are advantageous further by fixing the thermal head 6 to the side wall 2 b of the case main body 2 due to the side wall 2 b of the case main body 2 rigidity of the thermal head 6 can be reinforced as a result the rigidity of the thermal head 6 itself is not necessarily large and the thermal head 6 can be made thinner further the thermal head 6 is stiffly supported from its back surface by the side wall 2 b of the case main body 2 so the biasing force f due to the coil springs 9 can be directly used without being released as the pressurizing force of the thermal head 6 with respect to the heat sensitive paper 15 which is advantageous further in the embodiment the storing portion 2 c for storing the roll shaped heat sensitive paper 15 is provided to the inside of the substantially rectangular parallelepiped box shaped case 4 including the case main body 2 and the cover member 3 that close the case 4 so dead spaces s are defined in four corners thereof in the outward direction of a radius direction of the.