First and second selection signals for selecting one of print data and n pulse signals stored in a shift register are latched. The first or second selection signal is selected in accordance with an input selection information switching signal, and one of the n input pulse signals is selected based on the selected signal. A heat pulse selection circuit outputs the selected pulse signal as a heat pulse signal. The level of the selection information switching signal switches midway to switch the selected pulse signal. Parts of two pulse signals before and after switching are combined to generate a heat pulse signal.