PURPOSE: To provide an electrodeless discharge lamp lighting device, which can generate matching of a lamp with the lighting circuitry part and can light up the lamp in the optimum condition.

CONSTITUTION: A coil for lighting up 19 is installed in the neighborhood of the body 22 of the discharge lamp, and DC power emitted from a power supply circuit 4 is supplied to a high frequency conversion circuit 9 to prepare a high frequency power supply. The power therefrom is supplied to a lighting circuitry part 21 including the said lighting coil 19, wherefrom a high frequency power is fed to the lamp body 22 in magnetical coupling, to light up an electrodeless discharge lamp 17. The arrangement is further equipped with a sensor circuit to sense the electric power given by the power supply circuit 4, a comparator circuit 29 to compare the sensing value from this sensor circuit with the reference value, and control circuits 32, 33 which generate matching of the high frequency power supply with the lamp load by the lighting circuitry part 21 on the basis of a comparison signal given by the comparator circuit 29 and make control so that the power fed to the lamp body 22 is always constant.