A medicinal composition for suppressing or preventing the metastasis of a malignant tumor, the composition comprising, as an active ingredient, at least one kind of vasoprotective agent selected from the following (i) to (iv): (i) angiotensin II receptor antagonist, (ii) HMG-CoA reductase inhibitor, (iii) ghrelin or its derivative, and (iv) adrenomedullin or its derivative; or a pharmacologically acceptable salt thereof.