An input protection circuit includes an inverting amplifier circuit which converts the potential of an input signal input in such a way that the potential of the input signal lies in the input range of the potential range of a signal inputtable to an IC internal circuit. One protection diode is connected to a virtual ground node between an input resistor and an operational amplifier and a positive power-supply terminal to allow the input signal which has excessively exceeded the input range on the positive power-supply terminal side to flow toward the positive power-supply terminal, and another protection diode is connected to an arbitrary point between an input terminal and the input resistor and a negative power-supply terminal to allow the input current of the input signal which has excessively exceeded the input range on the negative power-supply terminal side to flow toward the input terminal from the negative power-supply terminal, thereby protecting the IC internal circuit.