The invention provides a novel adrenomedullin derivative sustainable for a long period which is capable of substantially suppressing unwanted side effects while maintaining pharmacological effects of adrenomedullin. In an exemplary embodiment, the invention relates to a compound represented by formula (I): A-CH2-B (I) [wherein A is a modifying group comprising one or more polyethylene glycol groups, and B is a peptide moiety derived from adrenomedullin or a modified form thereof with adrenomedullin activity, wherein the peptide moiety B is linked to the other moieties through a covalent bond of the nitrogen atom of the N-terminal α-amino group of the peptide moiety B to the carbon atom of the methylene group] or a salt thereof, or a hydrate thereof.
