Scattering on analysis in a multi-capillary electrophoresis apparatus is suppressed. The multi-capillary electrophoresis apparatus has a multi-capillary array that has a sample and a separation medium for separating a sample charged therein, and has a sampling section formed at ends of the capillaries and a detector part for acquiring information depending on the sample thus separated, a means for applying a voltage between the sampling section and the detector part, a chamber part having an air blowing mechanism and a temperature controlling mechanism, a capillary housing base provided on a leeward side of the air blowing mechanism and housing the multi-capillary array, and a first straightening plate provided between the chamber part and the capillary housing base.