A therapeutic or prophylactic agent for diabetes includes a thiazolidine derivative as a PPAR-γ agonist as an effective component which exhibits a reduced side effect of the PPAR-γ agonist. The therapeutic or prophylactic agent for diabetes includes a particular IP agonist such as beraprost sodium (BPS), and a thiazolidine derivative such as pioglitazone or a pharmaceutically acceptable salt thereof. Since the therapeutic or prophylactic agent exhibits a sufficiently effective hypoglycemic action without being accompanied by side effects characteristic to PPAR-γ agonists, the agent is useful as a highly safe and effective therapeutic or prophylactic agent for diabetes.
