To provide a bag which is constituted of plural bag bodies separable and independently usable and has unified design of good appearance before separating bag bodies without imperfect feeling like a part of the outside face of each bag body is missing and a bad form when the bag bodies are separated.

A sub-bag body 2 detachable from the main bag body 1 by an open fastener 3 and a sub-case 11 with a front wall plate 13 and a rear wall plate 14 detachable by an open fastener 12 are provided to enable the main bag body 1 to be separated from the sub-bag body 2. The sub-case 11 is separated into the front wall plate 13 and the rear wall plate 14. Thus the separated front wall plate 13 and the separated rear wall plate 14 of the sub- case 11 are made connectable with the separated main bag body 1 or the sub- bag body 2 respectively by engaging separated one side half parts 12a, 12b of the open fastener 12 respectively with separated one half parts 3a, 3b of the main bag body 1 or the sub-bag body 2.