To provide a sensor mounting structure which enables mounting an automotive sensor directly to the wall section of a part to be detected, without using screws, and also mounting a pressure detector directly to a pressure air passage without using a pressure inlet pipe. The non-circular sensor mounting hole is provided for inserting a part of the sensor housing into the wall section of the part to be detected. In the sensor housing the first locking portion (pawl) and the second locking portion (flange) are integrally formed by molding. The housing 1 is allowed to be inserted into the mounting hole under the condition that the pawl is directed to a specific orientation, and, after insertion, is turned through a specific angle. Therefore the pawl is engaged on the inside surface of the wall section. The flange is engaged on the outside surface of the wall section The pawl and the flange are designed to hold the wall section of the part to be detected, thereby mounting the sensor. The projection of the hook is engaged with the recess provided in the sensor housing 1, thus locking the sensor from turning.