A deposition mask package comprising: a receiving portion; a lid portion that faces the receiving portion; a deposition mask that is arranged between the receiving portion and the lid portion and has an effective region in which a plurality of through-holes is formed, wherein the receiving portion has a first opposing surface facing the lid portion and a concave portion provided on the first opposing surface, the concave portion is covered with a first flexible film, and the effective region of the deposition mask is arranged on the concave portion with the first flexible film interposed therebetween, wherein the deposition mask and the concave portion have a longitudinal direction and a width direction orthogonal to the longitudinal direction, and rectangular shape, when viewed along a normal direction of the deposition mask, the longitudinal direction of the concave portion extends along the longitudinal direction of the deposition mask, the normal direction extends along a stacking direction of the deposition mask and the first flexible film, the overall length of the concave portion in the longitudinal direction is smaller than the overall length of the deposition mask in the longitudinal direction, and ends on both sides in the longitudinal direction of the deposition mask are arranged on the first opposing surface of the receiving portion, wherein when viewed along the normal direction of the deposition mask, a dimension of the concave portion in the width direction is larger than a dimension of the deposition mask in the width direction, and wherein an interposed sheet is interposed between the deposition mask and the first flexible film, a dimension of the interposed sheet in the width direction is smaller than the dimension of the concave portion in the width direction, the dimension of the interposed sheet in the width direction is larger than the dimension of the deposition mask in the width direction, and an overall length of the interposed sheet in the longitudinal direction is larger than the overall length of the deposition mask in the longitudinal direction. a receiving portion; a lid portion that faces the receiving portion; a deposition mask that is arranged between the receiving portion and the lid portion and has an effective region in which a plurality of through-holes is formed, wherein the receiving portion has a first opposing surface facing the lid portion and a concave portion provided on the first opposing surface, the concave portion is covered with a first flexible film, and the effective region of the deposition mask is arranged on the concave portion with the first flexible film interposed therebetween, wherein the deposition mask and the concave portion have a longitudinal direction and a width direction orthogonal to the longitudinal direction, and rectangular shape, when viewed along a normal direction of the deposition mask, the longitudinal direction of the concave portion extends along the longitudinal direction of the deposition mask, the normal direction extends along a stacking direction of the deposition mask and the first flexible film, the overall length of the concave portion in the longitudinal direction is smaller than the overall length of the deposition mask in the longitudinal direction, and ends on both sides in the longitudinal direction of the deposition mask are arranged on the first opposing surface of the receiving portion, wherein when viewed along the normal direction of the deposition mask, a dimension of the concave portion in the width direction is larger than a dimension of the deposition mask in the width direction, and wherein an interposed sheet is interposed between the deposition mask and the first flexible film, a dimension of the interposed sheet in the width direction is smaller than the dimension of the concave portion in the width direction, the dimension of the interposed sheet in the width direction is larger than the dimension of the deposition mask in the width direction, and an overall length of the interposed sheet in the longitudinal direction is larger than the overall length of the deposition mask in the longitudinal direction.