Disclosed is a container bag for containing particulate materials, which is prevented from being barreled and retained in a stable erect state when contents fill the container bag, whereby the container bag can maximize the loadage of the particulate materials within a limited space with stability. The container bag includes lateral walls, the particulate materials filling an inner space defined by the lateral walls, a bottom wall formed generally in a quadrangle shape and connected to the bottom ends of the lateral walls, a cover connected to the top ends of the lateral walls, and hoops connected to the top ends of the lateral walls, the cover, the lateral walls and the bottom wall being formed from a flexible material, wherein each side of the quadrangle-shaped bottom wall is recessed at the central area thereof.