PURPOSE: To obtain an electric dust collecting device constituted so that charge timing is not superposed, by applying intermittently a DC high voltage which controls the electric conduction of a thyristor, to plural dust collecting electrodes.

CONSTITUTION: With respect to the voltage supplied between dust collecting electrodes 6a, 6b from an AC power source 1, the electric conducting state of a thyristor part 2 is controlled intermittently by a damping device 3. The control device 3 consists of a trigger circuit 3A, a diode matrix 3B and an outputting circuit 3C. The outputting circuit 3C constitutes a driver by connecting transistor elements 17AW17N whose base sides are connected to output lines A, B, C...N of the diode matrix 3B. Photocouplers 8a, 8b of the thyristor part 2 are turned on and off by biasing in the forward direction between the emitter and the base of said transistor elements 17AW17N, and in the reverse direction between the base and the collector. In this way, the timing of each power source supplied to each dust collecting electrode is selected through the diode matrix 3B, and the thyristor 2 is controlled as desired.