PURPOSE: To eliminate the need for a conventional sensor for detecting an original point of movement and simplify a device, by detecting the original point of movement of a printing head by utilizing a vertical sensor for setting a printing gap, and a horizontal sensor for detecting the kind of a paper.
CONSTITUTION: A serial printer comprises a vertical sensor 11 for detecting the vertical position of a printing head 2 and a horizontal sensor 18 for detecting an identification mark 27 or the like provided on a paper 16, the sensors being provided on a carrier 3 on which the printing head 2 is supported. The serial printer is provided with a white reference region 20 for the horizontal sensor 18, at an end part of a platen 1 on the home position side. Thus, a boundary 22 at which brightness is changed is provided between the white region part 20 and a grey or black main body part 21 of the platen. A shielding plate 14 for shielding the vertical sensor 11 in a region in which the horizontal sensor crosses the boundary 22 is attached to a stationary member, and the timing of a change in an output from the horizontal sensor 18 under the condition where the vertical sensor 11 is shielded is made to be the timing of detection of an original point of movement.