1. A capillary electrophoresis apparatus having: a capillary; an optical irradiation system which irradiates the capillary with excitation light; and an optical detection system comprising: a wavelength dispersion device configured to disperse fluorescent light from the capillary along a direction perpendicular to the capillary axis, a two-dimensional detector configured to detect a fluorescence spectrum image acquired from the wavelength dispersion device, and a multi-bandpass filter having a plurality of predetermined discontinuous wavelength transmission regions, wherein: the multi-bandpass filter cuts off the fluorescent light having a wavelength longer than a predetermined long-wavelength edge and the fluorescent light having a wavelength shorter than a predetermined short-wavelength edge, the multi-bandpass filter has at least one discontinuous cutoff region between the predetermined long-wavelength edge and the predetermined short-wavelength edge, the two-dimensional detector is a two-dimensional charged coupled-device device (CCD) camera configured to form images from the capillary in the wavelength dispersion direction and the capillary axis direction, the capillary axis direction being orthogonal relative to the wavelength dispersion direction, the optical detection system calculates an integrated value of a signal of the fluorescence spectrum for each of the wavelength transmission regions of the multi-bandpass filter, and excitation light irradiating the capillary propagates in the capillary axis direction.