In a conventional gear coupling, since an end cover is attached to a sleeve, lubricant has sometimes leaked out through the joint between the sleeve and the end cover. A gear coupling includes: a pinion having external teeth, and fixed to a first rotary shaft; a sleeve having an opening at each end thereof through at least either one of which the pinion is introduced into the inside thereof and internal teeth meshed with the external teeth of the pinion, and fixed to a second rotary shaft; a first end member having a rotary shaft space through which the first rotary shaft passes, for closing over the sleeve opening through which the first rotary shaft passes; and a second end member for closing off the other opening, wherein the sleeve, the first end member, and the second end member are configured to form a space for retaining the lubricant, the gear coupling has the sleeve and the first end member, or the sleeve and the second end member that are integrally formed.