The invention relates to a drum drill for drilling an anchor rod, and belongs to the technical field of a foundation fixation building in soil layer drilling. The drum drill comprises a drum drill body and a drill bit, wherein a first through hole which passes through in the axial direction is formed in the drum drill body; a sliding casing is arranged inside the first through hole; a hole expanding blade is arranged on the casing; a base is manufactured at one end of the casing; a second through hole is formed in the base; an opening is formed in a side wall of the casing. During use, the casing slides and is completely fed into the first through hole, one end of the casing is in sealed meshing with the other end of the drum drill body, then the casing and the drum drill body can rotate synchronously; meanwhile water flows through the second through hole and the first through hole in sequence and is ejected out from the first through hole; when the base and the opening completely slide off the first through hole, the hole expansion blade extends outside the sleeve from the opening, and at the same time the water flows through the second through hole and the opening in sequence and is ejected out from the opening. The drum drill is simple in overall structure and reliable in action, and drilling, hole expansion, grouting and drill bit withdrawing can be completed at one time.