To obtain a battery driven thermal transfer printer by employing a porous surface recording medium as a recording sheet and an employing a thermal head comprising heating elements arranged in line on a basic material having low thermal conductivity thereby saving power required for saturation recording.

A porous surface recording medium 2 is produced by laminating a porous surface plastic sheet 2b of 10 and several μm thick having multiple pores of 1-25μm diameter to a plain paper or a synthetic paper basic material 2a. At the time of printing, an ink ribbon 1 is brought into tight contact with a recording sheet 2 (porous surface recording medium) and fed between a thermal head 10 and a platen roller 3. Subsequently, a plunger 4 is conducted to clamp the ink ribbon 1 and the recording sheet 2 by means of the thermal head 10 and the platen roller 3. Under that state, a current is fed from a drive IC to the heating element in the thermal head 10 to generate heat for fusing the ink in the thermal head 14 thus performing thermal transfer printing onto the recording sheet 2.