PURPOSE: To reduce the burden of the power supply section of a thermal printer device capable of obtaining the photographic printing of an intermediate tone, and to acquire a printed picture having an inconspicuous streak.

CONSTITUTION: An output Q from a line memory 13, in which image gradation data are stored, and an output P from a gradation counter 14 representing the transmission of the data of any number of cell while using an output from a line start pulse generating circuit 9 as a reference are compared by a comparison circuit 12, and electricity is conducted through a thermal head 1 when Q≤P holds. Accordingly, a conduction time is equally divided before and after while employing the half time of the period of one line as a reference, thus reducing the burden of a power supply section, then obtaining a printed picture having an inconspicuous streak.