To provide a gear grinding tool capable of being mounted in a compound machine tool, grinding a gear to high precision in a short time, and reducing its manufacturing costs by achieving the integration of the gear grinding operation with other machining operations and reductions in equipment investments, machining time, and the time required for movement between processes, etc.

The gear grinding tool A which is mounted in a compound machine tool includes a tool body shaft 6 with a tapered shank 6a mounted in a mounting hole 4 in a tool shaft 2; a worm grinding wheel 7 mounted at the end of the tool body shaft 6; and a casing 8 rotatably supporting the tool body shaft 6 on each side of the wheel 7 and having an abutting portion 30 made to abut against the end face 1a of a tool head 1 when the tapered shank 6a is mounted in the mounting hole 4.