A method comprising at least a step (1) of preparing a silane master batch by melt-kneading, all or part of a polyolefin resin, an organic peroxide, an inorganic filler containing a metal hydrate and a metal carbonate, and a silane coupling agent, at a temperature equal to or higher than the decomposition temperature of the organic peroxide, and a step (3) of mixing the silane master batch and a silanol condensation catalyst or a catalyst master batch; a heat-resistant silane crosslinked resin molded body and a heat-resistant silane crosslinkable resin composition prepared by the method, and a silane master batch and a heat-resistant product.