Bag-manufacturing device

Provided is a bag-manufacturing device with a simple configuration that: prevents fluctuations in tension, slippage of seal positions, and meandering or skewing of the film material; allows the setting of precise initial conditions; reduces or makes unnecessary monitoring during continuous movement, and time and structures for adjustment; allows increased film material feed rate; and improves production efficiency. The bag-manufacturing device (100) for packaging containers that seals prescribed areas of a film material (F) comprises: a tension-controlling means (165) for controlling the continuous feed rate according to the values detected by a tension sensor (164) of a tension-detecting roll (163); an optical detection means (140) for simultaneously recognizing multiple marks (M) provided on the surface of the film material (F) at the respective positions thereof; a skewing correction means (150); and a seal position-correcting means (180) for adjusting the positions of multiple sealing means (171) in the f