Disclosed is a system that senses the pressure of a suction cap and automatically performs injection. The present invention comprises: a suction motor for increasing the suction pressure to the suction cap of a suction injection needle a solenoid valve having a solenoid valve controller connected thereto and having the function of relieving the suction pressure of the suction cap a pressure sensor having a drug injection controller connected thereto and measuring the pressure of the suction cap a drug injection motor operated by the drug injection controller on the basis of the pressure of the suction injection needle measured by the pressure sensor a screw gear bolt connected to a syringe piston pusher which pushes a syringe piston along the lengthwise direction of a drug injection supporting portion a screw gear shaft passing through the screw gear bolt and rotating according to the operation of the drug injection motor and a connecting member for interconnecting the solenoid valve, the suction motor, the pressure sensor, and the suction injection needle. Thus, after the suction cap is attached to the skin, the pressure is sensed and a set amount of drugs is automatically injected. Therefore, the accuracy of drug treatment can be increased.
