To provide a small and inexpensive Hall element type pressure sensor excellent in linearity.

The inventive pressure sensor comprises a diaphragm 1 being flexed upon receiving a pressure to be measured, a first magnet 4 secured to the diaphragm, a second magnet 8 of same polarity secured oppositely to the first magnet 4, and a Hall element 9 comprising a Hall IC disposed between first and second magnets. The diaphragm 1 is provided with a central opening and substantially disc-like shape having inner circumferential part secured with the first magnet 4 and outer circumferential part being fitted fixedly in the case 5 of the pressure sensor. Consequently, the diaphragm is held in the case 5 without being supported by other resilient body. The diaphragm 1 has a beam structure of even strength where a plurality of rows of constant thickness part having circumferential width decreasing gradually and from the inner and outer circumferential sides toward radial center and a thin part of small thickness are arranged alternately and radially along the circumferential direction.