To make a work site range and a dangerous place easily recognizable to a passerby and a driver of a vehicle by enabling an incandescent lamp to automatically repeat full wave lighting and half wave lighting in a cone light incorporating the incandescent lamp.

When an AC power source AC is closed, a TRIAC 23 is lighted by a half wave by a rectifying diode D1, and puts an incandescent lamp 9 in a half wave lighting condition. A signal generating circuit 21 outputs a square wave in a preset period since a DC power source is supplied simultaneously when the AC power source AC is closed, and controls ON/OFF of a photocoupler. This photocoupler 22 lights the TRIAC 23 by a full wave in the vicinity of a zero-crossing point of the AC power source AC. When the photocoupler 22 is put in an ON condition, the TRIAC 23 is lighted by a full wave, and a full wave of the AC power source AC is supplied to the incandescent lamp 9. When switches 6 and 20 are put in an open condition, the TRIAC 23 is controlled through the photocoupler 22 by the output of a signal generating circuit 21, and half wave and full wave lighting of the incandescent lamp 9 is automatically repeated.