A pressure sensor, comprising a sensor unit including a cylindrical housing having an inner peripheral portion, a sensor chip having a signal processing electronic circuit unit and being adapted for detecting a pressure and sending a detection output signal, a supporting member supporting the sensor chip on one end portion of the supporting member , an insulator between an outer peripheral surface of the supporting member and an inner peripheral surface of the housing , a diaphragm supported by the housing and configured for partitioning a liquid sealing chamber from a pressure chamber in a face to face relationship with the liquid sealing chamber, the liquid sealing chamber being formed in the inner peripheral portion of the housing between the diaphragm and the one end portion of the supporting member and an end surface of the insulator , in which liquid sealing chamber the sensor chip is placed, and a group of input-output terminals electrically connected to the sensor chip and to the supporting member , further comprising an electric field blocking member placed between one end surface of the sensor chip in the liquid sealing chamber and the diaphragm , characterized in that the electric field blocking member has fixing end portions and is supported by the supporting member with the fixing end portions attached at the one end portion of the supporting member so as to have the same electric potential as the electric potential of the one end portion of the supporting member for blocking an electric field acting on the signal processing electronic circuit unit of the sensor chip , and the electric potential of the one end portion of the supporting member supporting the sensor chip and the electric potential of the electric field blocking member are an electric potential equal to an electric potential of the signal processing electronic circuit unit of the sensor chip . a sensor unit including a cylindrical housing having an inner peripheral portion, a sensor chip having a signal processing electronic circuit unit and being adapted for detecting a pressure and sending a detection output signal, a supporting member supporting the sensor chip on one end portion of the supporting member , an insulator between an outer peripheral surface of the supporting member and an inner peripheral surface of the housing , a diaphragm supported by the housing and configured for partitioning a liquid sealing chamber from a pressure chamber in a face to face relationship with the liquid sealing chamber, the liquid sealing chamber being formed in the inner peripheral portion of the housing between the diaphragm and the one end portion of the supporting member and an end surface of the insulator , in which liquid sealing chamber the sensor chip is placed, and a group of input-output terminals electrically connected to the sensor chip and to the supporting member , further comprising an electric field blocking member placed between one end surface of the sensor chip in the liquid sealing chamber and the diaphragm , characterized in that the electric field blocking member has fixing end portions and is supported by the supporting member with the fixing end portions attached at the one end portion of the supporting member so as to have the same electric potential as the electric potential of the one end portion of the supporting member for blocking an electric field acting on the signal processing electronic circuit unit of the sensor chip , and the electric potential of the one end portion of the supporting member supporting the sensor chip and the electric potential of the electric field blocking member are an electric potential equal to an electric potential of the signal processing electronic circuit unit of the sensor chip . <EOS>