PURPOSE: To perform correct printing even though the lines of ruled line printing are increased, in printing the ruled lines, by separately inputting character data and ruled line data, inputting the next line data when a CR code is found in advance, and continously performing the printing of the ruled lines or the characters.

CONSTITUTION: Under the contol of a buffer control part 20, the first line of a printing code buffer 11 is set in buffers 14, 15, and 16 and the second line is set in buffers 17, 18, and 19, separately. Namely, upper ruled line data 2, printing data 31, 32, and 33, and lower ruled line data 2 are set separately. At the same time, printing instruction codes (CR, NL, and the like) are set in a registers 12 and 13. When the upper ruled line data 2 is located in the buffer 14, the upper ruled line is printed. When the register 12 is CR, the buffer 17 is further checked. When the ruled line data 2 is located in the buffer 17, the upper ruled line is consecutively printed. When the register 13 is CR, the next line data is read by the code buffer 11. When it is the ruled line data, it is set in the buffer 17. In an example (a), since the register 13 is NL, the upper ruled line is changed after printing, and the data in the buffer 15 is printed.