PRINTER

PURPOSE:To ensure that a printing head is constantly positioned within the width of a printing medium, by outputting a moving quantity for moving the printing head in a spacing direction according to the with of the printing medium fed to a printing part, to a spacing driving part. CONSTITUTION:When a printing medium 4 is set to a tractor 12 and a paper- supplying command T is given to a controlling part 10, the tractor 12 is driven, and a leading end part of the medium 4 is moved as indicated by an arrow D, on which the width of the medium 4 is detected through an output signal from a detector 7, a moving quantity L is outputted from a calculating part 8 to a spacing driving part 5, and a printing head 1 is moved in a spacing direction by the moving quantity L by the part 5. Next, a platen 2 is driven to feed the medium 4. Accordingly, the head 1 is constantly positioned at a predetermined position according to the width of the printing medium 4 by moving the head 1 in the spacing direction.