To provide a method for producing a terpene and/or allylphenol-based polymer, advantageous in industrial production.

The method for producing the terpene and/or allylphenol-based polymer involves polymerizing the terpene-based compound having a carbon-carbon double bond, and/or the allylphenol, or a mixture of the terpene-based compound having the carbon-carbon double bond, and/or the allylphenol, with other additionally polymerizable unsaturated compound in a basic hydrogen peroxide aqueous solution under heating.