An optical waveguide element includes: an optical waveguide including an organic non-linear optical material; a first electrode arranged on one surface side of the optical waveguide; a second electrode arranged on another surface side of the optical waveguide; a protective member disposed on the second electrode, the protective member including (i) a third electrode which is provided on a first surface of the protective member, the first surface facing the second electrode, the third electrode being electrically connected to the second electrode, (ii) a fourth electrode which is provided on a second surface of the protective member, the second surface opposing the first surface, and (iii) a conductive portion which penetrates through the protective member from the first surface to the second surface, and electrically connects the third electrode and the fourth electrode.