The invention relates to a device and method for repairing a manhole cover. The device comprises a positioning device, a milling and planing device and a drive device. The method for repairing the manhole cover comprises steps as follows: (1), the manhole cover is taken down; (2), the positioning device is clamped on the inner edge of an outer ring; (3), an annular protective baffle is arranged; (4), the milling and planning range of a movable cutter bit is adjusted; (5), a positioning shaft is matched with a positioning hole; (6), an engine is started for milling and planing; (7), milling and planing are performed until a needed depth is obtained; (8), the engine is stopped; (9), a manhole cover base and waste on an asphalt layer on the periphery of the manhole cover are taken out simultaneously; (10) leveling is performed and then compacting is performed after filling. Compared with the prior art, the device replaces a conventional air compressor and a grooving machine, and low noise is realized; mechanization is adopted almost in the whole process, and the device is very efficient and reduces labor intensity of a worker; the drive device comprises the engine, a hydraulic pump and a hydraulic motor and is energy-saving and low in cost; the manhole cover is attractive and smooth during later compacting due to leveling during milling and planing.