Abstract: A container inner bag mounted in a freight container and filled with a large amount of content, which is made of a synthetic resin sheet and has an elongated rectangular parallelepiped shape and a pentahedral or hexahedral structure. The elongated rectangular parallelepiped-shaped container inner bag is cut along at least ridge portions formed between the front and rear walls and the left and right side walls. These walls are adapted to be joined and separated along the ridge portions by connecting and separating means such as a fastener, respectively. The front wall has, at the upper portion, a cut portion adapted to form a content insertion opening through which the content is filled into the bag, and, at the lower portion, a cut portion adapted to form a content takeout opening through which the content is taken out from the bag. These cut portions are adapted to be joined and separated by connecting and separating means such as a fastener, respectively.