An adjustable respirator shell, suitable for being worn on a human body trunk, includes a body, a belt and a buffer. The body includes a protrusive portion and a contact portion. The protrusive portion has an opening connecting a fluid pressure controller, and the contact portion is to contact the human body trunk. The belt, connecting the body, is to surround the human body trunk so as to fasten the adjustable respirator shell on the human body trunk. The buffer covers a circumference of the contact portion, and the contact portion contacts the human body trunk via the buffer. In addition, the buffer includes at least one cushion.