The invention relates to the lens barrel injection-molded product cutting device. And in the tool horn, the compressed air is exhausted and the state where the lens barrel is fixed among the process where the lens barrel settled in the seating jig with the exhausting pressure power of the compressed air cuts ultrasound in the tool horn the generate and with proper place is maintained. In that way it induces so that the lens barrel is not interfered in the vibration of ultrasound and the failure rate generation of the lens barrel is prevented and accordingly the product competitiveness through the productivity improvement is intensified but the state has the purpose. For this, as for the lens barrel injection-molded product cutting device in which the seating jig, which is the lens barrel injection-molded product including the lens barrel, the runner and gate placed and seating jig and engagement are made and including the tool horn in which the separation is comprised ultrasound between the generate and the lens barrel and runner with the cutting by the vibration of ultrasound of the invention, it comprises the pneumatic air-blower furnace which prevents that it provides the compressed air provided in the tool horn from the outside to the lens barrel settled in the seating jig and it is not interfered in the ultrasound of the tool horn with the exhausting pressure power of the compressed air and it maintains the state where the lens barrel is fixed and the lens barrel is damaged.