A pressure sensor includes a sensor chip and a circuit chip. The sensor chip, which is configured to generate an electrical signal representative of a pressure being sensed, has a surface including a sensing area and a plurality of electrical contact pads disposed on the surface. The circuit chip includes a circuit configured to process the electrical signal and has a surface on which a plurality of electrical contact pads of the circuit chip are disposed. The circuit chip is joined to the sensor chip so that the electrical contact pads of the circuit chip are respectively electrically connected to those of the sensor chip, all the electrical contact pads of the circuit chip and the sensor chip are hermetically sealed and isolated from the fluid, and the surfaces of the circuit chip and the sensor chip face each other with the electrical contact pads of the same interposed therebetween.