PURPOSE: To obtain a cross-linker masterbatch which can carry a highly volatile silane cross-linker in a high concn. stably for a long term.

CONSTITUTION: This silane cross-linker carrier, used for cross-linking a thermoplastic polymer, contains as the main components a foamed resin comprising either an ethylene copolymer having a content of a carbonylated comonomer of 30wt.% or higher and a melt flow rate of 10 or lower or a mixture comprising the ethylene copolymer and a vinyl polymer and having a content of the carbonylated comonomer of 30wt.% or higher and a liq. silane cross-Tinker comprising a compd. having a methylene group at one end and a hydrolyzable condensable tri-substd. silyl group at the other end. The cross-linker is carried in a content of 30-90wt.% by the foamed resin.