To provide a machining device for a liner insertion hole capable of repairing a damaged liner insertion hole.

The shaft center of rotation driving means rotating a tool and the center of the liner insertion hole of the cylinder block are matched to each other so as to machine a liner support part of the liner insertion hole of the cylinder block. A tool feed mechanism is provided. The tool feed mechanism is provided also with a tool release mechanism and the tool can be moved to an appropriate machining position without rotating the tool. The tool is fixed to an adapter exchangeable relative to the machining device so as to be adjusted the radial position of the liner insertion hole of the tool by the adapter. The adapter is provided with a fine boring machining tool preset master gage. The machining device is provided with a liner measuring mechanism for the liner insertion hole.