The invention relates to an improvement on a production machining device and method of a trolley case, in particular to an ultrasonic welding machining device and method for a thermoplastic trolley case. A case shell is arranged in clamps on the two sides. A corner armor is arranged at an inner bent position of the case shell. A bent clamp abuts against the inner side of the lower portion of the corner armor. An ultrasonic welding head is arranged on the outer side of the portion, provided with the corner armor, of the case shell. The ultrasonic welding head is arranged on an ultrasonic vibrator. The ultrasonic vibrator is arranged below an air cylinder. By the adoption of the ultrasonic welding machining device and method for the thermoplastic trolley case, the connection strength between the corner armor and the trolley case shell is improved, the overall mechanical strength of the trolley case is improved, the production efficiency is improved, and cost is reduced. After assembly is conducted by the adoption of the ultrasonic welding machining device and method for the thermoplastic trolley case, each corner of the case shell is firm and stable and not prone to deformation, and the trolley case has better mechanical performance; and meanwhile, the production efficiency is improved, and the production cost is reduced.