A first and a second signal line respectively supplying a first potential and a second potential to one end of a capacitive load, a waveform output circuit whose input terminal is connected to a supply line supplying a third potential, whose output terminal is connected to the first or the second signal line, and whose control terminal is connected to a waveform generating circuit, and a reactive current preventing switch connected between the control terminal and the output terminal or the input terminal of the waveform output circuit are provided. During a period when a reactive current is prevented from flowing, the reactive current preventing switch is bought into conduction to make a potential difference between the control terminal and the output terminal of the waveform output circuit smaller so that the waveform output circuit cannot be operated, which prevents the reactive current from flowing, leading to an improvement in the reliability of a driving circuit.