Fluorescence detector

The improved fluorescence detector comprises a tubular electrophoretic device through which a sample labelled with four kinds of fluorescent dye is caused to migrate, illumination optics for illuminating the tubular electrophoretic device with exciting light and detection optics for detecting the fluorescence emitted from the sample illuminated with the exciting light and it is characterized in that a plurality of tubular electrophoretic devices (1) are arranged in a row, a plurality of graded-index lenses (9) are arranged parallel to and in the same number as said plurality of tubular electrophoretic devices (1), each lens array being composed of four vertically stacked graded-index lenses, a plurality of bandpass filter arrays (11) are also arranged parallel to and in the same number as said plurality of electrophoretic devices (1), each filter array being composed of four filters arranged vertically in a row, and a light-receiving element of a planar type (13) is provided at the back of the rows of said bandpass filters (11). The apparatus is an efficient and compact multi-color fluorescence detector capable of real-time detection.