A method for producing a rubber composition crosslinked to a crosslinking degree of 50% or higher by mixing a crosslinkable rubber (A) and a thermoplastic resin (B) and crosslinking the mixture with a crosslinking agent (C), wherein the crosslinking agent (C) is divided and added in parts to sequentially carry out the crosslinking in which the crosslinking is carried out to a crosslinking degree of 5-45% by the first addition of the crosslinking agent (C) and furthermore the crosslinking is carried out to a crosslinking degree of 50% or higher by further addition of the crosslinking agent (C).