PURPOSE: To ensure that a page on which printing is to be started is always set on the face side, by a method wherein the folding direction at a perforation of a paper when folding the paper is detected, and page feeding is conducted by a printing-controlling means in accordance with an electrical detection signal.

CONSTITUTION: A detecting mechanism for the folding direction of a perforation detects the condition of a continuous paper 3, and the number of perforations between a perforation located on the upper side of a printing mechanism part 1 and a perforation located on the lower side of the mechanism 4 is calculated on the basis of the number of lines on one page of the paper 3 which number is set in a controller. When the number of perforations thus calculated is an odd number and the paper is in the condition on the front side A, printing is started directly in this condition, and when the paper is in the condition on the rear side B, printing is started after feeding one page. When the number of perforations is an even number, the operations for the conditions A, B are reversed.