To enable to detect machining of a case containing electronic devices from outside.

A protecting apparatus 11 for electronic devices comprises an upper case 12 and a lower case 14. Anomaly detecting plates 16 and 18 are integrally fixed to the inside of the upper case 12 and the lower case 14 respectively by insert molding. A circuit board 20 is contained in the lower case 14 and is fixed in such a way that its top is covered by the upper case 12. Semiconductor memory devices 22 such as memory chips or MPU's having memory areas as electronic devices are soldered onto the circuit board 20. A conductive pattern 24 is formed on the surface of the anomaly detecting plates 16 and 18. A specified current passes through the conductive pattern 24. When the conductive pattern 24 is cut by machining from the outside, the current is interrupted and anomaly detecting signals are outputted.