Disclosed is a method for ditecting urothelial cancer in a simple manner and with high accuracy. Specifically disclosed is a method for detecting urothelial cancer, which comprises administering 5-aminolevulinic acid (ALA), a derivative thereof, or a salt of the compound or the derivative to a subject, collecting urine from the subject, and determining the presence or amount of a fluorescence in a cell contained in the urine collected from the subject.