To enable the quantification of neutral fat or cholesterol contained in respective blood plasma lipoproteins by simple manipulation.

A sample solution is treated with a hydrolase, a fat-soluble dye is added, the blood plasma lipoproteins are fractionated by electrophoreses, to measure the coloring intensities of the obtained bands. The quantities of the neutral fat or the cholesterol contained in the blood plasma lipoproteins corresponding to the respective bands are determined from the coloring intensities of the band obtained after the electrophoreses. As the hydrolase, lipoprotein lipase or cholesterol esterase is used. Preferably, the electrophoreses is carried out using an electrophoreses chip having a plate, a gel formed on the plate, partitioning walls dividing the gel into a band pattern, and recesses formed on the surfaces of the divided gels.