An evanescent light generation element for oscillating evanescent light from an optical waveguide to a clad layer, including a 0.1 μm-10 μm thin layer composed of a ferroelectric single crystal or oriented crystal having first and second principal surfaces, and incident side end and exit side end surfaces. A ridge optical waveguide is formed in the thin layer and extends between the incident and exit side end surfaces of the thin layer. At least a pair of grooves is formed on both sides of the ridge optical waveguide in the thin layer and opened at the first principal surface of the thin layer. A clad layer is provided on the first principal surface or the second principal surface. A width of the ridge optical waveguide at the exit side end surface is less than a width of the ridge optical waveguide at the incident side end surface.