An elastic member having an elastic sheet stretchable structure in which an elastic sheet is interposed between a first sheet layer having air permeability and a second sheet layer having air permeability, and the first sheet layer and the second sheet layer are bonded through joint holes penetrating the elastic sheet or via the elastic sheet at a plurality of sheet joined portions (40, 41) arranged at intervals, wherein a stretchable region exhibiting the elastic sheet stretchable structure is allowed to be stretched and contracted in a stretchable direction by a contraction force of the elastic sheet, the joined portions (40, 41) have first joined portions and second joined portions, a first joined portion row is formed such that the first joined portions are spaced along an alignment direction in which alignment is performed at an angle intersecting the stretchable direction in a range of 45 degrees to 135 degrees, the first joined portions in the first joined portion row are formed to have a length of 0.3 to 7.0 mm with respect to an orthogonal direction orthogonal to the stretchable direction, the first joined portion row is formed to have a formation pitch of 2.0 to 20.0 mm with respect to the stretchable direction, as a distance with respect to the orthogonal direction determined by a mutual relationship between the adjacent first joined portions in the first joined portion row, a ratio of (a separation distance (d) between adjacent first joined portions)/(a distance from one point of a joined portion to one corresponding point of an adjacent first joined portion) is 5 to 60% in percentage, a plurality of the first joined portion rows is formed at intervals in the stretchable direction, and a plurality of the second joined portions having a shorter length than a length of the first joined portions is formed in the alignment direction between the first joined portion rows. wherein a stretchable region exhibiting the elastic sheet stretchable structure is allowed to be stretched and contracted in a stretchable direction by a contraction force of the elastic sheet, the joined portions (40, 41) have first joined portions and second joined portions, a first joined portion row is formed such that the first joined portions are spaced along an alignment direction in which alignment is performed at an angle intersecting the stretchable direction in a range of 45 degrees to 135 degrees, the first joined portions in the first joined portion row are formed to have a length of 0.3 to 7.0 mm with respect to an orthogonal direction orthogonal to the stretchable direction, the first joined portion row is formed to have a formation pitch of 2.0 to 20.0 mm with respect to the stretchable direction, as a distance with respect to the orthogonal direction determined by a mutual relationship between the adjacent first joined portions in the first joined portion row, a ratio of (a separation distance (d) between adjacent first joined portions)/(a distance from one point of a joined portion to one corresponding point of an adjacent first joined portion) is 5 to 60% in percentage, a plurality of the first joined portion rows is formed at intervals in the stretchable direction, and a plurality of the second joined portions having a shorter length than a length of the first joined portions is formed in the alignment direction between the first joined portion rows.