PURPOSE: To set a bag easily in a container and prevent the fluid in the bag from leaking out within the container by a method wherein the bag is partially made of a specific laminate film and a lid is provided for covering the opening part at the lower end of the container or a fluid discharging member at the upper end thereof in a freely attaching and detaching manner.

CONSTITUTION: A lid body 5 is removed from the opening part at the lower end of a container body 4 and then attached to the upper end thereof in such a manner as to cover a fluid discharging member 6. In this condition, the container body 4 is turned upside down and held in a standing position and, from the lower opening part set upward, a bag 1 is placed into the container body 4 with its bottom part 3 facing toward below. At this time, the bottom part 3 is pierced with a tube 7. Since the bottom part 3 of the bag 1 is made of a specific laminate film, it does not tear. Thereafter, the lid body 5 is removed to uncover the fluid discharging member 6 of the container body 4 and is placed back on its lower opening part and the container body 4 is turned back in the regular standing position so that the fluid discharging member 6 is set in the upper position.