The present invention is directed to prevent the stretching caused by the wear of the annular restis for suspending a plurality of dust collecting electrode plates and remain the long life of the annular restis. A mobile electrode(18)of an electric dust collector comprises a pair of annular restis which can be rotatablely supported on a pair of driving wheels(20)respectively, and a plurality of dust collecting electrode plates(26)which are suspended on the pair of annular restis and rotatablely moves surrounding the discharge electrode along a given direction. The mobile electrode is characterized in that the annular restis is made of flexible annular metal wire(24). A plurality of coupling segment parts are desired to be formed around the circumferential of the driving wheels(20)at equalpitch, and coupling blocks which coupling with the coupling segment parts are arranged on the annular metal wire(24)at equal pitch.