To provide a hydrocarbon reforming/trapping material which is capable of adsorbing and reforming a hydrocarbon. A hydrocarbon reforming/trapping material of the present invention has an SiO2/Al2O3 ratio of from 7 to 12, and contains an Fe(II)-substituted beta zeolite which is ion-exchanged by Fe(II) ions. The amount of supported Fe(II) is preferably 0.001-0.5 mmol/g with respect to the Fe(II)-substituted beta zeolite. This Fe(II)-substituted beta zeolite is suitably produced by dispersing and mixing a beta zeolite having an SiO2/Al2O3 ratio of from 7 to 12 in an aqueous solution of a water-soluble compound of divalent iron, and mixing and stirring the solution, so that Fe(II) ions are supported on the beta zeolite.