An optical waveguide structure capable of optically coupling a surface type optical device, such as a surface emitting laser diode or a photodiode, and a transmission medium, such as an optical fiber, located so that their light output surface and light input surface will form an angle of about 90.degree. with each other simply and easily. The optical waveguide structure comprises a first clad section having a curved surface for gradually turning the direction in which light travels almost squarely and a groove formed in the curved surface along the direction in which light travels, a core section which is made from a transparent material with a refractive index higher than the refractive index of the first clad section and with which the groove is filled in, and a second clad section which covers an exposed surface of the core section and the curved surface of the first clad section and which is integrated with the first clad section.