There is provided a pressure measuring sensor having a diaphragm including a peripheral fixing portion so formed as to be fixed to a pressure measuring sensor proper and be thick, a pressure receiving portion responsive to a pressure to be measured to move, and a strain causing portion responsive to the movement of the pressure receiving portion to cause strain, the pressure receiving portion having a shape so formed as to substantially perform the same function as a member having a high rigidity when moving in response to a change in the above described pressure to be measured, and the strain causing portion being substantially subject to bending stress in response to the movement of the pressure receiving portion moved according to the change in the above described pressure to be measured and thereby the strain causing portion providing a plurality of gauge resistors formed on the strain causing portion with tensile stress or compressive stress proportionate to the pressure to be measured.