PURPOSE: To obtain an amylin coagulation inhibitor useful for preventing and treating diabetes, containing, as active ingredient, a hydroquinone or quinone compound.

CONSTITUTION: This amylin coagulation inhibitor contains, as active ingredient, 1-70 (pref. 5-50)wt.% of a hydroquinone or quinone compound of formula I, II or III. Using an appropriate vehicle etc., this inhibitor can be manufactured into pharmaceutical preparations in the form of an oral agent such as capsules, tablets, granul-es, powder, suspension, liquid, or syrup, an injection, suppository, or agent for external use. The hydroquinone or quinone compound has activity to inhibit amylin coagulation, therefore inhibiting cytotoxicity due to amylin coagulation and being useful for preventing and treating diabetes (esp. type II diabetes, diabetes with glucose tolerance depression, obesity, insulin-resistant diabetes).