PURPOSE: To improve the printing quality and processing capability by setting a couple of paper sensors by sensing whether a printing paper is present or not on a paper carrier path and setting the clearance between the printing head and the paper to a value corresponding to the thickness of the printing paper in compliance with the state of whether the corners of the paper are present or not.

CONSTITUTION: A paper, for example, an envelope 17 is set on a paper receiver by an operator, and the paper is inserted from the direction indicated by arrow A along a left guide 25. Whether the paper is present or not is sensed by paper sensors 15 and 16. When the presence of paper is sensed, a feed roller (disposed opposite to a roller 11) and a roller (disposed opposite to a roller 13) are rotated to start carrying the paper. When the recording paper is the envelope 17, the thickness of a flap section 17b and the thickness of sections 17b-17e other than the flap section are different, and the clearance between a printing head and the paper is adjusted so that the section 17e is located on the position where the printing head is brought into contact with the paper.