A waveform of the output signal having high reproducibility to an input signal is outputted from capacitive load. Even the driving device is configured as a switching amplifier and drives capacitive load. Reactive power can be reduced to perform low power consumption. Output signals V 1 a and V 1 b that an output signal Vcap 1 across output terminals 50 and 51 of load C 1 fed back to input terminals 9 a and 9 b are compared with an input signal Vin so that error between output signals V 1 a and V 1 b is detected. A first error suppression signal Vout 1 is produced so as to suppress the detected error between signals. The proportion of a first duration T 1 that electric power is supplied to the load C 1 to a second duration T 2 that no electric power is supplied and load C 1 is floated is altered according to the first error suppression signal.