PURPOSE: To attain a bar code printing system with high freedom by inputting data on a character code string and data on a printing size, calculating the width of a bar while referring to the prescribed correspondence table and outputting printed data in said width.

CONSTITUTION: The data on the character code string where character codes are arrayed as separate characters with respect to a character string to be outputted, and the printing size data specifying the size of a bar code at the time of printing are inputted and stored in an I/O information storing means 10. By referring to the table associating a bar code pattern with a character code stored in a bar code pattern information storing means 20, a printed data generation means 30 calculates the widths of the thin and thick bars of the bar code to be outputted from the reference result and the printing size data, outputs a bar code pattern as printed data expressed by the thin and thick bars in the calculated widths, and stores said pattern in an output data storage file 200. If printing is carried out according to the output data, a bar code complying with instructions is printed.