In a semiconductor pressure detecting device, residual stress due to die bonding between pedestal seat and base member as well as stress due to welding between base member and cap are reduced. The semiconductor pressure detecting device comprises a semiconductor sensor element having a thin-walled pressure-receiving portion, a pedestal seat, a base member and a cap, wherein pressure fluid is introduced to a pressure chamber via pressure fluid introducing holes of the base member and the pedestal seat so that pressure of the fluid is detected by the semiconductor sensor element. Outer peripheral configuration of the bonding surface of the pedestal seat to the base member is rectangular shaped, and bonding length in the direction of the diagonal line of the rectangular shape is set based on a prescribed maximum operating pressure of the semiconductor pressure detecting device, conditions for generation of residual strain during a bonding process between the pedestal seat and the base member and conditions for generation of strain during a bonding process of the cap to the base member.