Abstract: A sleeping bag is provided which is free from the problems of the bag body slipping off an air mattress laid therebeneath, the air pillow slipping off the bag body, etc. so that there is no fear of comfortable sleep being disturbed. The bag body 1 is composed of a mattress portion 1a and a coverlet portion 1b. The mattress portion 1a and the coverlet potion 1b are joined to each other so that the coverlet potion 1b is folded over the mattress 1a. The insides of the mattress portion 1a and the coverlet portion 1b are stuffed with cotton or feather paddings having the adiabatic property. The other sides of the respective mattress portion and the coverlet portion as well as the foot ends thereof are provided with slide fasteners 1c continuously therealong so that a generally envelope shaped structure is formed.