The present invention provides a modified atrialnatriuretic peptide that exhibits prolonged duration timein blood and maintains cGMP elevating activity. Thepresent invention provides a modified peptide in which atleast one sugar substance is linked directly through aglycosidic bond or via a linker structure to at least onehANP peptide, or a pharmaceutically acceptable saltthereof, a medicament comprising the modified peptide orthe salt thereof as an active ingredient, etc.