A biochip substrate capable of realizing the high detection accuracy by restricting a nonspecific adsorption or bonding of a substance to be detected, when used for a detection or analysis of protein, nucleic acids and the like. The biochip substrate is for fixing a biologically active substance on a surface of a solid substrate, and characterized in that it has a layer comprising a polymer compound obtained by copolymerizing an ethylenically unsaturated polymerizable monomer having an alkylene glycol residue, an ethylenically unsaturated polymerizable monomer having a functional group for fixing a biologically active substance and an ethylenically unsaturated polymerizable monomer having a cross-linkable functional group, on the surface of the substrate.