A switching amplifier is disclosed and comprises: a power supply (Vcc); input circuits (Va, Vb); switch transistors (M1, M2) connected with each other in series; driving circuits (I1, I2) coupled with the switch transistors (M1, M2) respectively; a bootstrap circuit for supplying operation voltage to the driving circuit (I1). The switching amplifier also comprises: leakage circuits (M1a, M2a) or auxiliary switching circuits (M1′, M2′). With the switching amplifier of the invention, the fluctuation of the bootstrap potential can be suppressed and the signal distortion of the switching amplifier can be prevented.