Abstract: A vane type valve timing adjustment device used in an internal combustion engine, wherein a plurality of vanes are formed radially and integrally from a boss portion of a vane rotor and a stopper portion able to contact a housing side is formed at a specific vane among these. Since a large stress acts at the root portion where the specific vane connects with the boss portion, stress is prevented from concentrating at the root portion by chamfering the corner or forming a connecting part with a large radius of curvature or a nonmachined surface, surface hardened surface, etc. to increase the strength.