A cross optical waveguide structure includes a first optical waveguide, a second optical waveguide, and an intersection portion positioned in the same plane. The first optical waveguide includes a first fixed-width portion, a second fixed-width portion, a first tapering portion, and a second tapering portion. The second optical waveguide includes a third fixed-width portion, a fourth fixed-width portion, a third tapering portion, and a fourth tapering portion. The intersection portion is linked to the first to the fourth tapering portions having such a tapering shape that a mode field radius of the light input to the first fixed-width portion, the second fixed-width portion, or the third fixed-width portion, and the fourth fixed-width portion is reduced by the first tapering portion, the second tapering portion, the third tapering portion, the fourth tapering portion, respectively, and the light is collected in the intersection portion.