In a pressure detecting device for a vehicle, a first detection member is fixed to a sensor housing such that a first surface of a first diaphragm faces a closed space of the vehicle and a first chamber isolated from the closed space is provided to face a second surface of the first diaphragm. A second detection member is fixed to the sensor housing such that a first surface of a second diaphragm faces the closed space, and a second chamber is provided to face a second surface of the second diaphragm. When the first diaphragm and the second diaphragm are deformed by the same amount and in the same direction, the first detection member and the second detection member output signals having the same value with opposite signs. The first surface of the first diaphragm and the first surface of the second diaphragm are covered with a protection member.