To provide a shoulder belt which is easily attachable/detachable, easily adjustable in length, and storable when unused and a bag using the shoulder belt.

The shoulder belt comprises two sets of components, one set comprising a belt, a reel member with one end from which the belt can be wound up or drawn out, a reel support member rotatably supporting the reel, and a connecting member attached to the reel support member for connecting a connecting part set on a bag. The two sets are connected to the other end of each belt. A length adjusting mechanism for adjusting the length of the belt between two reel members is provided.