To provide an electronic lock used for a dead bolt of a cylinder lock, which is inexpensive, simple and small in size, can be naturally used for a new lock and can also be additionally installed to an existing lock as an accessory, in view of the current state of slow development of crime preventive countermeasures (installing two keys) against the drastic increase in social problems such as a picking offense and a thumb-turn turning crime.

A power supply, an emergency power supply, a CPU built-in receiver and a solenoid coil are arranged and fixed to near the tip end part of the dead bolt inside a wall side strike washer receiving box. When radio waves transmitted by a CPU of a remote controller from outside is received, the plunger of the solenoid coil of the arranged and fixed mechanism is moved in and out to hold or release the dead bolt.