To provide a mask with improved convenience.

The mask M comprises: a mask body 1 which is rectangular as seen from the top; a front upper crease 10, the crease being parallel to the upper end edge of the mask body 1, disposed between the center of the mask body 1 and the upper end edge of the mask body 1; a right upper joint part 30; a left upper joint part 20; a right lower joint part 50, and a left lower joint part 40. A region B of the upper end edge of the mask body 1 in the right upper joint part 30 and a region A of the upper end edge of the mask body 1 in the left upper joint part 20 are separate from each other so that the right upper joint part 30 and the left upper joint part 20 do not cross each other. A region C of the lower end edge of the mask body 1 in the right lower joint part 50 and a region D of the lower end edge of the mask body 1 in the left lower joint part 40 are separate from each other so that the right lower joint part 50 and the left lower joint part 40 do not cross each other.