A piezoelectric sensor comprising: a piezoelectric element for detecting a pressure; an integrating circuit that integrates a current signal outputted from the piezoelectric element to convert the current signal into a voltage signal, the integrating circuit being constituted by an integrating operation amplifier, a charging capacity and a discharging resistor; an amplifier circuit that amplifies an output from the integrating circuit to output thereof to outside; and a reference voltage source that prescribes an offset voltage of an output signal outputted from the amplifier circuit; characterized in that: further comprising: a writable memory that stores information for setting an amplification factor of the amplifier circuit; and a connection terminal portion, located at an end portion of a sensor housing, which includes an external-connection connector provided with three user terminals for supplying the power, the GND and the output signal, and a writing terminal for writing the information to the memory; wherein the integrating operation amplifier, the amplifier circuit, the reference voltage source and the memory are contained in a single integrated circuit; and the writing terminal is separated from the three user terminals. a piezoelectric element for detecting a pressure; an integrating circuit that integrates a current signal outputted from the piezoelectric element to convert the current signal into a voltage signal, the integrating circuit being constituted by an integrating operation amplifier, a charging capacity and a discharging resistor; an amplifier circuit that amplifies an output from the integrating circuit to output thereof to outside; and a reference voltage source that prescribes an offset voltage of an output signal outputted from the amplifier circuit; characterized in that: further comprising: a writable memory that stores information for setting an amplification factor of the amplifier circuit; and a connection terminal portion, located at an end portion of a sensor housing, which includes an external-connection connector provided with three user terminals for supplying the power, the GND and the output signal, and a writing terminal for writing the information to the memory; wherein the integrating operation amplifier, the amplifier circuit, the reference voltage source and the memory are contained in a single integrated circuit; and the writing terminal is separated from the three user terminals. a writable memory that stores information for setting an amplification factor of the amplifier circuit; and a connection terminal portion, located at an end portion of a sensor housing, which includes an external-connection connector provided with three user terminals for supplying the power, the GND and the output signal, and a writing terminal for writing the information to the memory; wherein the integrating operation amplifier, the amplifier circuit, the reference voltage source and the memory are contained in a single integrated circuit; and the writing terminal is separated from the three user terminals. the integrating operation amplifier, the amplifier circuit, the reference voltage source and the memory are contained in a single integrated circuit; and the writing terminal is separated from the three user terminals.