To provide a coil structure having sufficient sensitivity for rumbling a gate, concerning improvement of a tuning circuit used for a rumbling article monitoring device used for preventing shoplifting of a commodity or the like by being stuck to a commodity case or the commodity itself and for a non- rumbling article monitoring device storable in a tag case having the same-shaped appearance as a tag case of the rumbling article monitoring device.

This article monitoring device having the tuning circuit of 7.5-9 MHz and comprising a case for storing the commodity, the tag case mounted on the case, for locking the commodity in the case at the storing time, an antenna coil installed in the tag case, and a capacitor connected to the coil, or a device formed by winding a coil having the thickness of 0.4 mm-1.0 mm on a ferrite core having the length of 3-12 mm as the coil in the tag case mounted on the commodity and incorporating a rumbling tag rumbling when dismantled, is used.