Abstract: A coupling device according to the present invention includes: a first coupling member having first teeth on a disk surface; a second coupling member having second teeth on the disk surface; and a fastening member fastening the first coupling member and the second coupling member at central portions. A reference surface is a surface parallel to the disk surface. A tooth surface angle is an acute angle formed between a tangent line of the meshing tooth surface and a reference surface at a point C on an intersection line between the reference surface and the meshing tooth surface of the first tooth and the second tooth, in a cross section perpendicular to a radial direction of the first coupling member. Tooth surface angles ? and ? of the first tooth change along the radial direction of the first coupling member.