A pressure sensor comprising: a sensor unit including a housing, a sensor chip for detecting a pressure and sending a detection output signal, a chip mounting member supporting the sensor chip, a diaphragm supported by a lower end surface of the housing for partitioning a liquid sealing chamber, in which the sensor chip is placed, from a pressure chamber facing the liquid sealing chamber, and a group of input-output terminals supported by a hermetic glass and electrically connected to the sensor chip; the housing, the hermetic glass, the chip mounting member, and the diaphragm forming the liquid sealing chamber; and an electric field blocking member placed between one end surface of the sensor chip in the liquid sealing chamber and the diaphragm, and for blocking an electric field acting on a signal processing electronic circuit unit of the sensor chip, wherein the electric potential of the electric field blocking member is set to the same electric potential as that of the electronic circuit of the sensor chip, characterized in that the electric field blocking member is strip-shaped and comprises a trench-shaped portion facing the one end surface of the sensor chip and passing immediately above a central part of the sensor chip with a predetermined clearance, and first and second fixing portions (48B, 48C) continued to both end portions of the trench-shaped portion, and an oil filling pipe is press-fitted into a hole in the first fixing portion, the group of input-output terminals projecting from the end surface of the hermetic glass are inserted into holes (48f, 48d) and a notch portion of the second fixing portion, the electric field blocking member is electrically connected to one of the group of input-output terminals, and the first and second fixing portions (48B, 48C) are supported on an end surface of the hermetic glass. a sensor unit including a housing, a sensor chip for detecting a pressure and sending a detection output signal, a chip mounting member supporting the sensor chip, a diaphragm supported by a lower end surface of the housing for partitioning a liquid sealing chamber, in which the sensor chip is placed, from a pressure chamber facing the liquid sealing chamber, and a group of input-output terminals supported by a hermetic glass and electrically connected to the sensor chip; the housing, the hermetic glass, the chip mounting member, and the diaphragm forming the liquid sealing chamber; and an electric field blocking member placed between one end surface of the sensor chip in the liquid sealing chamber and the diaphragm, and for blocking an electric field acting on a signal processing electronic circuit unit of the sensor chip, wherein the electric potential of the electric field blocking member is set to the same electric potential as that of the electronic circuit of the sensor chip, characterized in that the electric field blocking member is strip-shaped and comprises a trench-shaped portion facing the one end surface of the sensor chip and passing immediately above a central part of the sensor chip with a predetermined clearance, and first and second fixing portions (48B, 48C) continued to both end portions of the trench-shaped portion, and an oil filling pipe is press-fitted into a hole in the first fixing portion, the group of input-output terminals projecting from the end surface of the hermetic glass are inserted into holes (48f, 48d) and a notch portion of the second fixing portion, the electric field blocking member is electrically connected to one of the group of input-output terminals, and the first and second fixing portions (48B, 48C) are supported on an end surface of the hermetic glass.