Abstract A novel waveguide-coupled prism device as a surface plasmon resonance sensor has been developed. The waveguide was fabricated by depositing Ag, SiO 2 , and Au thin films in this order on a prism. The device demonstrated a sharp absorption in the light reflectance curve due not only to the insertion of polarized light where electric field was parallel to the reflection plane (P-wave) but to that perpendicular to the reflection plane (S-wave). The experimental reflectance curves for both P- and S-waves were well predicted by the Fresnel formulas. The former and the latter absorptions are due to surface plasmon resonance and the attenuation of propagating light through the waveguide by the repetitive absorption at the metal/SiO 2 boundary, respectively.