Provided is a method and apparatus for measuring a urea concentration. The method includes adding a first reagent comprising a hypohalite ion, preferably a hypofluorite ion, a hypochlorite ion, a hypobromite ion, or/and a hypoiodite ion, and a second reagent comprising a xanthene dye, preferably rhodamine B, fluorescein, dibromofluorescein, dichlorofluorescein or/and a rare earth fluorescent complex to a sample solution including urea to be allowed to undergo a reaction, and measuring light intensity of chemiluminescence produced through the reaction to determine the urea concentration, preferably in real time, in the sample solution comprising spend dialysate during hemodialysis. The apparatus for measuring a urea concentration, the apparatus comprising a second-reagent adding unit comprising a second reagent (21) tank, a pump (15) and a liquid feeding path (10) configured to add a second reagent comprising a xanthene dye or a rare earth fluorescent complex to a sample solution comprising urea to be mixed together to form a mixed solution (21)； a first-reagent adding unit comprising a first reagent (22) tank, a pump (16) and a liquid feeding path (11) configured to add a first reagent comprising a hypohalite ion to the mixed solution to be allowed to undergo a reaction in a reaction cell (2)； and a measuring unit comprising an optical detector (5) and a measuring device (7) configured to measure light intensity of chemiluminescence produced through the reaction to determine the urea concentration.
