To make peel-off of a junction of a sensor chip hardly occur.

A differential pressure sensor 200 is provided with a sensor chip 3 joined onto a wall surface 1-1a of a partition wall 1-1 positioned on the side of a first space 1-2, so that one face 3-1a of a sensor diaphragm 3-1 faces a first pressure-receiving diaphragm 2-1 and so that a communication passage 3-3 linking to the other face 3-1b of the sensor diaphragm 3-1 communicates with a penetration passage 1-4 of the partition wall 1-1. In the differential pressure sensor 200, the sealing pressure of a first pressure transmitting medium 5-1 sealed in a first sealing chamber 6-1 is made higher than that of a second pressure transmitting medium 5-2 sealed in a second sealing chamber 6-2. Thus, damage due to a back pressure is reduced and peel-off of junctions 4-1, 4-2 is hard to occur.