The effects of copper plate surface-treatment with 3-aminopropyltriethoxysilane (APS) on the adhesion between the copper plate and polyethylene plate through polyethylene gel have been investigated by tensile shear test, DSC measurement, and FT-IR measurement. The copper plate was treated with an ethanol-water mixed solvent containing water content of 30 vol% as a solvent of the APS, the polysiloxane structure favorable for the adhesion between polyethylene and copper plate is formed rapidly. The interfacial shear strength goes up to over 8 MPa when treated with the APS solution in concentration of about 5.0 x 10(-2) mol l(-1). The flexible polysiloxane networks formed from the APS solution on copper plate were found to act effectively for the adhesion. Experiments for model substances corresponding to the interphase in the present adhesion on the basis of DSC measurement and FT-IR measurement have revealed that the flexible polysiloxane networks formed from the APS solution and polyethylene chains as an adhesive interpenetrate and interact.