An ear hook member (20a, 120a) for a mask, where the ear hook member (20a, 120a) has an annular sheet shape and has, in a plan view thereof, a first direction corresponding to an up-and-down direction of the mask and a second direction orthogonal to the first direction, the ear hook member (20a, 120a) comprising: a first surface material; a second surface material that is disposed on an opposite side to the first surface material; and a plurality of stretchable string materials (9, 9t, 9s, 9w) between the first surface material and the second surface material, the plurality of stretchable string materials (9, 9t, 9s, 9w) being spaced from each other in the first direction and respectively extending along the second direction, wherein each of the stretchable string materials (9, 9t, 9s, 9w) is adhered to the first surface material and the second surface material, with the stretchable string materials (9, 9t, 9s, 9w) being stretched, the ear hook member (20a, 120a) has a shape of a tetragonal ring and includes an upper-side portion and a lower-side portion that respectively correspond to an upper side and a lower side of the tetragonal ring, the ear hook member (20a, 120a) includes, as viewed in the first direction: an upper-end region corresponding to a region over which the upper-side portion extends; a lower-end region corresponding to a region over which the lower-side portion extends; and a middle region between the upper-end region and the lower-end region, characterized in that one or more of thicknesses, stretch rates, and intervals of the plurality of stretchable string materials (9, 9t, 9s, 9w) are different between the middle region and a region that is either or both of the upper-end region and the lower-end region wherein the ear hook member (20a, 120a) comprises one or more of following additional features (i) to (iii), namely: (i) thicknesses of the stretchable string materials (9, 9t, 9s, 9w) used in the upper-end region and in the lower-end region are larger than thicknesses of the stretchable string materials (9, 9t, 9s, 9w) used in the middle region; (ii) stretch rates of the stretchable string materials (9, 9t, 9s, 9w) used in the upper-end region and in the lower-end region are larger than stretch rates of the stretchable string materials (9, 9t, 9s, 9w) used in the middle region; and (iii) intervals at which the stretchable string materials (9, 9t, 9s, 9w) are disposed in the upper-end region and in the lower-end region are shorter than intervals at which the stretchable string materials (9, 9t, 9s, 9w) are disposed in the middle region. a first surface material; a second surface material that is disposed on an opposite side to the first surface material; and a plurality of stretchable string materials (9, 9t, 9s, 9w) between the first surface material and the second surface material, the plurality of stretchable string materials (9, 9t, 9s, 9w) being spaced from each other in the first direction and respectively extending along the second direction, wherein each of the stretchable string materials (9, 9t, 9s, 9w) is adhered to the first surface material and the second surface material, with the stretchable string materials (9, 9t, 9s, 9w) being stretched, the ear hook member (20a, 120a) has a shape of a tetragonal ring and includes an upper-side portion and a lower-side portion that respectively correspond to an upper side and a lower side of the tetragonal ring, the ear hook member (20a, 120a) includes, as viewed in the first direction: an upper-end region corresponding to a region over which the upper-side portion extends; a lower-end region corresponding to a region over which the lower-side portion extends; and a middle region between the upper-end region and the lower-end region, characterized in that one or more of thicknesses, stretch rates, and intervals of the plurality of stretchable string materials (9, 9t, 9s, 9w) are different between the middle region and a region that is either or both of the upper-end region and the lower-end region wherein the ear hook member (20a, 120a) comprises one or more of following additional features (i) to (iii), namely: (i) thicknesses of the stretchable string materials (9, 9t, 9s, 9w) used in the upper-end region and in the lower-end region are larger than thicknesses of the stretchable string materials (9, 9t, 9s, 9w) used in the middle region; (ii) stretch rates of the stretchable string materials (9, 9t, 9s, 9w) used in the upper-end region and in the lower-end region are larger than stretch rates of the stretchable string materials (9, 9t, 9s, 9w) used in the middle region; and (iii) intervals at which the stretchable string materials (9, 9t, 9s, 9w) are disposed in the upper-end region and in the lower-end region are shorter than intervals at which the stretchable string materials (9, 9t, 9s, 9w) are disposed in the middle region. (i) thicknesses of the stretchable string materials (9, 9t, 9s, 9w) used in the upper-end region and in the lower-end region are larger than thicknesses of the stretchable string materials (9, 9t, 9s, 9w) used in the middle region; (ii) stretch rates of the stretchable string materials (9, 9t, 9s, 9w) used in the upper-end region and in the lower-end region are larger than stretch rates of the stretchable string materials (9, 9t, 9s, 9w) used in the middle region; and (iii) intervals at which the stretchable string materials (9, 9t, 9s, 9w) are disposed in the upper-end region and in the lower-end region are shorter than intervals at which the stretchable string materials (9, 9t, 9s, 9w) are disposed in the middle region.