Abstract: An object is to provide a method for completely and fully dehalogenating an organic halide through electrolysis, and an electrolysis apparatus used therefor. One embodiment of the invention is a method wherein, when carrying out dehalogenation by electrolyzing an organic halide or a liquid containing the organic halide, a diaphragm electrolytic cell in which an anode and a cathode are separated is used, and electrolysis is carried out while applying ultrasonic waves using ultrasonic wave generating means and stirring using stirring means, and an electrolytic cell used therefor. Another embodiment of the present invention is a method wherein, when carrying out electrolysis, a hydrogen-absorbing metal or alloy is used as a cathode. In this case also, it is preferable to further use a diaphragm electrolytic cell, and carry out electrolysis using ultrasonic wave generating means and stirring means.