A milling head has a body, a holding device, a driving axle, a spraying device and a tool adaptor. The body has a base, a rear cover, a front cover, a bearing seat and a middle liner ring. The holding device is connected to the body and has a linking arm, a mounting jacket, a bottom cap, a positioning shaft and a locating spring. The driving axle is rotatably mounted in the body and has a transmission shaft and a driving bevel gear. The spraying device is mounted on the base and has a mounting cover and an spraying ball. The tool adaptor is rotatably mounted in the base below the spraying device and has a transmitting bevel gear, a holding head and a connecting segment.