A method for measuring thyroglobulin(s), comprising using each one or more kinds of proteins capable of binding to a constant region of thyroglobulin(s) and proteins capable of specifically binding to a specific sugar chain structure of thyroglobulin(s) having the specific sugar chain structure, and the method of determining a malignancy of thyroid tumor, a reagent thereof using the obtained by the method for measuring thyroglobulin(s).
