To provide a hard bag capable of dispersing shock, though having no external difference from conventional bags.

A bag body has a structure composed of a core member made of a synthetic resin box continuously provided in one piece with a standing wall section which is formed in a square frame shape by being bent vertically from the circumferential edge, a cushioning material and an interior lining material arranged on the inner face side of the core member, and an exterior fly sheet material arranged on the outer face side of the core member, whereby the arranged materials are sewed up together along the opening sectional edge of the core member. One edge side of the bag body is hinge-connected to one side of a lid body by flexible connecting members, and other three sides of the bag body and other three sides of the lid body are each fitted with a slide fastener stringer capable of detaching mutual engagement. The lid body has a core member made of a synthetic resin and is arranged with the cushioning material and the interior lining material on the inner face and the exterior fly sheet material on the outer face side.