A lab-on-chip substrate includes a resin having a silicon content of 10% or less by weight as its base material and a hydrophilic polymer covalently bound onto the surface thereof by high-energy ray irradiation suitable for a protein-processing chip. The lab-on-chip substrate is resistant to washing and usable for an extended period of time without adsorption of proteins on the base material surface, i.e., a protein electrophoretic polymeric chip having a microchannel allowing high-accuracy analysis of trace amounts of proteins because of reduction in the amount of detection noise.