PURPOSE: To provide a culture medium for fluorescent detection which can detect groups of Escherichia coli in the specimen.

CONSTITUTION: The culture medium for fluorescent detection of colibacilli comprises 1 to 2.5wt.% of peptone, 0.25 to 0.5wt.% of sodium chloride, 0.4 to 0.6wt.% of yeast extract, 0.2 to 0.5wt.% of potassium hydrogen phosphate, 0.05 to 5wt.% of sodium pyruvate, 0.05 to 1wt.% of potassium nitrate, 0.01 to 1wt.% of sodium dodecylsulfate, and 4-methyl-umbellifer-β-D-galactoside or 4-methyl-umbellifer-β-D-glucuronide as a fluorescent substrate. The fluorescent substrate is preferably added to the culture medium in an amount of 10-14 to 10-2M. When cell groups of Escherichia coli are detected using the medium, the specimen is added to the medium, cultured at 30 to 44.5°C for several to teens hours, irradiated with a light of 365nm wavelength and measure the fluorescent light of 450nm wavelength.