PURPOSE: To improve the burglar preventing effect by providing a switch member closed when a regular magnet key is inserted into the key cylinder lock of a vehicle, and operating a feed element essential to the operation of an engine with a power feed signal via the switch member as information.

CONSTITUTION: When a regular magnet key 7 with multiple magnets g1, g2 on the upper piece section of a key main body 7a is inserted into the key hole 8 of a key cylinder lock 1, multiple magnet pin tumblers 9a, 9b stored across the inner hole of the outer tube member 2 and the inner tube member 5 of the key cylinder lock 1 are sprung up by the magnetic repulsion against a spring 10, and a magnetic sensitive switch 11 is closed. A power feed signal is sent from an on-vehicle battery 20 to an AND circuit 12 via the magnetic sensitive switch 11. When the magnet key 7 is rotated and a key switch 1A passes the on position, an output is generated from the AND circuit 12, and the control device 14 of an engine is set to the operation state.