The utility model discloses a screwing head of a handheld cap screwing machine. The screwing head of the handheld cap screwing machine comprises a screwing head body, a rubber sleeve and a fixing clamp. The screwing head body is formed by a hollow circular truncated cone and a hollow cylinder, the diameter of the small end of the hollow circular truncated cone is larger than or equal to that of the cylinder, and the small end of the hollow circular truncated cone is connected with one end of the hollow cylinder. The rubber sleeve is arranged in the hollow circular truncated cone of the screwing head body. The fixing clamp is arranged in the rubber sleeve, and the rubber sleeve is made to be in closed fit with the screwing head body. When the handheld screwing head of the cap screwing machine is used, a sample introduction bottle cap is placed in the rubber sleeve of the screwing head of the handheld cap screwing machine, the rubber sleeve is made to be contacted with the sample introduction bottle cap, and the driving force of the cap screwing machine is transmitted to the sample introduction bottle cap through friction. When the cap screwing machine rotates, the bottle cap is driven to rotate towards a tightening direction. Therefore, the time of the screwing operation of a sample introduction bottle can be greatly saved, and the fatigue of the fingers and the wrists of operating staff caused by long-term bottle cap screwing is avoided.