An electrophoresis fractionator comprises a multiplicity of separate cells (10, 11) provided on respective contact surfaces of two members (1, 2) which are in contact with each other movably relative to each other and move relative to each other to enable alternate switching between a position where the multiplicity of cells (10, 11) are connected to a single electrophoresis passage P together and a position where the multiplicity of cells (10, 11) are separated from one another, and electrodes (14, 15) provided on both respective ends of the electrophoresis passage P which is formed to be single.