To provide a relative pressure type pressure sensor of excellent water resistance by providing an air inlet hole on the bottom of a housing, providing a water reservoir space passage inside the housing, and bonding or ultrasonic- welding a base made of resin on the water reservoir space to cover the space.

For amplifying a microelectric signal to obtain sensor output voltage, a thick film integrated circuit board 2 forming an amplifying circuit adheres and fixes to a resin base 4 through soft adhesive, and a gauge assembly 1 and the thick-film integrated circuit board 2 are connected together through a wire 5. The resin base 4 is provided with a large atmosphere inlet hole outlet A9 for introducing the atmosphere on the gauge assembly 1 side through the atmosphere introducing hole A7 of a housing 6 and the water reservoir space 8. Hard adhesive 11 is spread on the adhesive groove of the housing 6 and hardened. Between the thick-film integrated circuit board 2 and a terminal 19, provided on the housing 6, is connected with an aluminum wire 12. The connector 16 of the housing 6 is provided with an atmosphere inlet hole outlet B16 for introducing the atmosphere from an atmosphere inlet hole B15 to a sensor inner space 17.