PROBLEM TO BE SOLVED: To provide a piperidine-1-oxyls-containing polymerization inhibitor composition in which the long-term stability of piperidine-1-oxyls easy to be deactivated in a solution state is improved, and capable of obtaining a stable polymerization inhibition effect over a long period, and a polymerization inhibition method for polymerizable olefins using the same.SOLUTION: Provided is a polymerization inhibition composition characterized in that one or more kinds of water-soluble metal salts are made to coexist in one or more kinds of piperidine-1-oxyls expressed by the general formula (1) or general formula (2), and also provided is a polymerization inhibition method for polymerizable olefins using the same.
