PURPOSE: To enable conversion of a printing characteristic of a recorder simultaneously with conversion of the number of gradations to be carried out by a more simple structure than a conventional structure according to a printing data to be inputted.

CONSTITUTION: A control part 1 having a plurality of signal wires outputting a binary and a gradation data, and a printer part 2 capable of printing in gradation a gradation data of a plurality of bits are provided. Further, a memory 3 equipped with a conversion table wherein output (a) of the control part is taken as an input, and output (d) of the same number as the number of input bits of the printer part 2 is provided, and a counter 7 wherein a dot clock is counted and selection signal (f) of the conversion table is outputted, are provided. A content of the conversion table is changed according to the number of gradations of an output data of the control part 1 to carry out conversion of the number of gradations.