A rounding machine for a reinforcing steel bar comprises a working table, a working disk, molds, a switch, a motor M, a transmission mechanism and a fixing seat; the transmission mechanism comprises a rotating shaft; the motor M is controlled by the switch to work; the rotating shaft of the transmission mechanism is controlled by the motor M to rotate; a hole is formed in the working table; the rotating shaft penetrates through the hole to be fixed to the working disk; the working disk rotates with the rotating shaft used as the center; the fixing seat is fixed on the working table; the molds comprise a first mold and a second mold; the first mold and the second mold are fixed on the working disk; the position, required to be rounded, of the reinforcing steel bar is clamped between the first mold and the second mold; and the other end of the reinforcing steel bar is fixed on the fixing seat. The whole machine is simple to operate and can be operated by only one person; and compared with traditional forging methods for bending reinforcing steel bar hooks, the machine has the advantages that the labor intensity of workers is greatly reduced, and the labor efficiency is improved.