PURPOSE: To automatically perform a uniform assignment work by a printer by providing a printer mechanism having a carrier placing an image read sensor and a printing head, and a printer control circuit having specific uniform assignment control means.

CONSTITUTION: A printer has a printer mechanism having a carrier 1 placing an image read sensor 2 and a printing head 3, and a printer control circuit having uniform assignment control means. The control means, when N pieces of printing data and print command are fed from a host system, moves, the carrier to a left end, stores the output of the sensor in a memory while moving the carrier rightward, obtains the position X1 of a ruled line 1 of vertical lines of left side of an area to be described on a sheet and the position X2 of a ruled line 2 of vertical lines of right side of the area to be described by referring to the content of the memory, edits received character strings with the printing position as X1 and the character pitch as (X1-X2)/N, and prints, after the editing is completed.