A pressure sensor includes a sensor housing mounted on a vehicle, a first detector located in the housing and having a first diaphragm facing a sealed space of the vehicle, a second detector located in the housing and having a second diaphragm facing the sealed space, and a protector located in the housing and covering the first and second detectors. A first chamber is formed between the first diaphragm and the housing and isolated from the sealed space so that the first diaphragm can be deformed by a pressure in the sealed space. A second chamber is formed between the second diaphragm and the sensor housing and communicates with the sealed space. The first and second diaphragms produce the same signal when being deformed by the same amount in the same direction.