PURPOSE: To provide a dot matrix data processing method capable of reducing the ROM capacity of a character generator to a large extent, by utilizing the characteristics possessed by a character font.

CONSTITUTION: In the constitutional diagram (b) of ROM of a character font (a) constituted of longitudinal and lateral dots each consisting of 16 rows, the upper rank two bits of each longitudinal row data having 16 rows are codes showing the characteristics of the data of said rows and can show four kinds of characteristics. In this embodiment, when all of the longitudinal rows are white dots, the code of '00' is allotted and, in the same case as the previous row data, the code of '01' is allotted and, when upper and lower two dots are white dots, the code of '10' is allotted and, when upper and lower four dots are white dots, the code of '11' is allotted and data quantity is reduced in such a state that, in the cases of '00' and '01', all data of the rows thereof are omitted and, in the case of '10', upper and lower two bits are omitted and, in the case of '11', upper and lower four bits are reduced and stored in succession to each code.