A release agent composition includes a poly(meth)acrylate (A) containing a structural unit (1) represented by the following formula (1); in which R1 represents hydrogen or a methyl group and R2 represents a long-chain alkyl group having 12 to 28 carbon atoms, a liquid polymer (B) and a crosslinking agent (C), wherein at least one of the poly(meth)acrylate (A) and the liquid polymer (B) has a reactive functional group, and the crosslinking agent (C) is a compound having a functional group capable of reacting with the reactive functional group.