A thermal trasfer printer including a thermal head, and a platen positioned against the thermal head through a printing sheet. The thermal head has a substrate formed of heat insulating material, at least one glaze layer on a top surface of the substrate extending longitudinally thereof, a plurality of heat generating elements on the glaze layer, a plurality of electrodes each connected to the heat generating elements in a manner to form an opening for the heat generating elements and a protective layer for preventing the electrodes and heat generating elements from contacting the printing sheet to avoid their wear. A portion of the protective layer for protectng the heat generating elements has a height which is greater by more than 5 .mu.m than the height of a portion of the protective layer for protecting the electrodes. The width of the glaze layer transversely of the substrate is less than 200 .mu.m at a location which is 10 .mu.m below a top surface of the portion of the protective layer for protecting the heat generating elements in a vertical direction. The platen is a flat platen and its deflection caused to occur by a biasing force exerted on the thermal is more than 0.02 time and less than twice as great as the height of the glaze layer.