To provide a mask less liable to cause a shift in wearing position. The mask includes a main-body portion for covering a lower face portion of a wearer and a fixation portion, coupled to the main body portion, for fixing the main-body portion to the lower face portion of the wearer. The main-body portion includes: a main-sheet portion; a lower body for holding a lower jaw of the wearer, the lower body being made of a stretchable material and provided across right and left end portions of the main-sheet portion on a lower, inner side of the main-sheet portion; and/or an upper body for holding the nose of the wearer, the upper body being made of a stretchable material and provided across the right and left end portions of the main-sheet portion on an upper, inner side of the main-sheet portion.