An inertia detecting transducer having a reliable detection element. The element is kept to be free from deposition of gas and organic substance generated from resin adhesive. A first case of the transducer has an opening and a circuit component mounted thereon, and is provided with an external electrode and a first connection electrode. A second case includes a detection element mounted inside thereof, and an opening of the case is sealed with a sealing plate. The second case is further provided with a second connection electrode. The second case is attached to the first case so that the former covers the opening of the latter. The second connection electrode and the first connection electrode are electrically coupled. In the above-described configuration of the present invention, if an inertia detecting transducer gets a partial damage, either one of the detection element and the circuit component remaining intact can be re-utilzed.