PURPOSE: To enable diagnosis of cancer by a method wherein glycoprotein in connection with cancer (TAG) in humors is made to react with a lectin and by measuring this, existence of cancer cells, proliferous extent and growth and decay thereof are known.

CONSTITUTION: A labeled lectin is added to humors to make reaction and the produced combination material between glycoprotein in connection with cancer and a labeled lectin or a nonreaction labeled lectin is separated, and this combined quantity of glycoprotein-labeled lectin or the quantity of the nonreaction labeled lectin is measured. As lectin labeled material, various kinds of enzyme, various kinds of fluorescent material and various kinds of radioactive material can be mentaioned.