It is intended to provide drugs for preventing, ameliorating and/or treating diabetes which contain as the active ingredient a plant−origin &bgr;(1→3) glucan having a molecular weight of from 5000 to 20000. These drugs for diabetes can be widely used either in IDDM or NIDDM, have little side effects, can exert effects even in case of oral administration without being affected by obesity, etc., can be widely employed as drugs for patients in various conditions, and are also usable as foods and drinks (medicinal foods, health foods, etc.) for patients of the above diseases, healthy persons or other animals. Also, a method of preventing, ameliorating and/or treating diabetes and use of the specific &bgr;(1→3) glucan as described above in these drugs are provided.
