To provide a light-weight bag for multi-purpose which carries required baggage to a destination and which plays a role of a cushion or a mat at the destination.

When the bag is folded in the state of housing matters, the bag consists of a front part 10, a back part 30, a bottom part 20, left and right side face parts 50 and 55, and a cover part 40. In its opened state, the bag forms a single square sheet of the front part 10, the back part 30, the bottom part 20 and the cover part 40. It is preferable that the front part, the back part, the bottom part, the left and right side face parts and the cover part consist of the three-layer structure of a front material, an inner core and an inner material, and that the inner core has heat insulating material.