To provide a power supply device for electric discharge lamps in which lamp extinguishing is completely prevented in high-pressure mercury vapor lamps with a comparatively large amount of mercury sealed within, is achieved through the use of a switchable connection from the connection state of a simulated arc discharge resistor (59) virtually equal to the arc discharge resistance of the high-pressure mercury vapor lamp to the connection state of simulated glow discharge resistors (59, 60) that have virtually 1/7 of the glow discharge resistance that is completed at the output terminal of the power supply device (2) for the electric discharge lamps in question. The simulated arc discharge resistor is connected to the power supply device for electric discharge lamps, and the simulated glow discharge current in the transient state, switched from the state of flow of simulated arc discharge current to the simulated glow discharge resistor, continues to be under 30% of the simulated arc discharge current for less than 10 .mu.s and the duration until the current recovers to at least 70% of said simulated arc discharge current is less than 100 .mu.s.