A switching amplifier of the invention boasts of an enhanced SN ratio in its output and an increased amplitude limit value in its input signal. The switching amplifier has a quantized signal generating section that converts an input signal to generate a quantized signal in the form of a PDM or PWM signal and a constant-current-outputting current amplification section that current-amplifies the quantized signal outputted from the quantized signal generating section. The quantized signal generating section and the current amplification section are formed by the same process. Another switching amplifier of the invention is inexpensive and is not affected by voltage fluctuations in the supply voltage. The switching amplifier has a quantized signal generating section that converts an input signal to generate a quantized signal in the form of a PDM or PWM signal, a constant-current-outputting current amplification section that current-amplifies the quantized signal outputted from the quantized signal generating section, and a feedback section for feeding a signal based on the output signal from the current amplification section back to the quantized signal generating section.