To provide an expression vector capable of making a high level production of a gene tic recombinant protein by using a mammalian cell as a host.

This expression vector which uses a promoter having low expression inductivity as a promoter in a plasmid and has a gene cistron of wasting neomycinphosphotransferase such as neomycimphosphotransferase cistron, etc., having an insertion sequence containing at least one couple of a sequence capable of coding an amino acid sequence between a sequence of the promoter and sector of a gene translation of the neomycintransferase and a multicloning site for gene integration having strong manifestation inducing promoter. This vector induces the high productivity of the genetic recombinant protein the hose mammalian cell. This vector preferably contains a gene cistron of dihydrofolic acid reducing enzyme using low expression inducing promoter as a promoter.