There are provided a resin composition capable of affording a cross-linked foam excellent in heat storage performance, a cross-linked product of the resin composition, and a method for producing the cross-linked product. Specifically, there is provided a resin composition containing an olefin polymer comprising a main chain containing monomer units derived from ethylene and branch chains having 5 or more carbon atoms, the number of the branch chains being within the range of 20 chains to 40 chains per 1000 carbon atoms constituting the olefin polymer, and having a melting peak temperature measured with DSC of within the range of 10° C. to 50° C., a crystallization peak temperature measured with DSC of within the range of 0° C. to 40° C., and a melt enthalpy measured with DSC of 50 J/g or more, and an olefin polymer having a melting peak temperature measured with DSC of within the range of 50° C. to 180° C.