To prevent foreign matter from penetrating into a thermosensitive heard part by providing a wiping member on the upstream side of a direction in which a recording medium is introduced with the thermosensitive head, and introducing the recording medium into a thermosensitive printer under such a state that a print face is kept in contact with the wiping member.

In a printer 10 which starts printing by introducing the tip of a recording medium P until it comes into contact with a thermosensitive head and a platen roller 2 and discharges the recording medium P from a discharging aperture 7 after printing, an attachment 50 for preventing foreign matter from penetrating is provided on the upper part of the printer 10. Consequently, when the recording medium P passes through a clearance between a wiping member 30 and a second guide sheet 52, both recording medium P and wiping member 30 are energized by appropriate force with the help of the elastic force of a first and the second guide sheet 51, 52, so that foreign matter sticking to a print face is wiped off by the wiping member 30. Thus it is possible to prevent foreign matter sticking to the print face of the recording medium P from penetrating into the printer 10.