PURPOSE: To light a direction indicating lamp with a stable and accurate period and to enable the detection of burn-out of lamp through an economical method.

CONSTITUTION: Upon closure of a switch for direction indicating lamp 1, a group of lamps 9 are immediately lighted if the output from microcomputer 3 is "0". After clapsing predetermined time the output from microcomputer 3 is brought to "1" to turn on the transistor Tr7 thus to open the B contact 12 of relay 2 and to turn off the group of lamps 9. Thereafter the filaments of said lamps 9 are gradually cooled to gradually decrease their resistances, thereby when the switch 1 is turned on under unlighting condition of the lamps to supply some current through a resistor 13 to the lamps 9, the terminal voltage of the groups 9 is gradually decreased. Said voltage is compared by a comparator 14 to detect any burn-out of the lamps from the comparison results.