A novel method of accurately assaying a glycoprotein by a simple procedure within a short period of time on the basis of a principle different from the existing enzymatic method. A method of assaying a glycoprotein in a sample which comprises treating the sample containing the glycoprotein with a protease, thus releasing glycopeptides (preferably alpha -glycopeptides and still preferably alpha -glycodipeptides) from the glycoprotein, treating these released glycopeptides with an oxidase, and assaying the hydrogen peroxide thus formed; and an assay reagent kit to be used in the enzymatic method.
