New method and apparatus for automatically producing a number of bag-shaped packages with a cap body integrally attached thereto and specific content filled at a high operational efficiency are disclosed. They are produced one by one using continuous thin flat film of synthetic resin as raw material by way of the steps of punching a cap body insert hole, inserting the cap body portion of the cap body into the punched hole, heat sealing it to the film, forming a tubular product, effecting longitudinal heat sealing, effecting transverse heat sealing of the lower end part of the tubular product to form a bag-shaped product, filling the latter with specific content, effecting transverse heat sealing of the upper end part of the content filled bag-shaped product and cutting off the latter along the center line extending between the adjacent products. Longitudinal heat sealing is generally effected while the film is displaced downward. Alternatively, longitudinal heat sealing may be effected while it is held immovably. Operation in each of the working sections is controlled by signals transmitted from a sensor adapted to detect the existence of one of marks printed on the film. Most of operations in the working sections are carried out while the film is held immovably.