A differential amplification circuit is constituted of a differential transistor pair including a pair of n-channel MOS transistors whose sources are connected together, a constant current source circuit which is connected to the sources of the differential transistor pair, a current-mirror load circuit including a pair of p-channel MOS transistors whose gates are connected together, and a bias generation circuit which generates a gate bias voltage and a drain bias voltage applied to the current-mirror load circuit in such a way that the same potential is set to both the drains of the p-channel MOS transistors. Thus, it is possible to reduce the input offset voltage without reducing the margin of operation voltage and without increasing the overall chip size.