Patent ID: 8105303

Claim:
A sheet member, comprising: a first sheet; a second sheet; and at least one elastic member having a shape selected from a thread shape, a net shape, a strip shape, and a sheet shape, arranged between the first sheet and the second sheet; wherein the first sheet comprises: a plurality of high-density regions; and a plurality of low-density regions, wherein the high-density regions alternate with the low-density regions in a predetermined direction, the elastic member is arranged in the predetermined direction in which the plurality of high-density regions alternate with the plurality of low-density regions, the elastic member in an expanded state is attached to at least a part of each of the plurality of high-density regions, and the following equation is satisfied: ( A+C )/ X≧A wherein A is a length of the high-density region, C is a length of the low-density region, and X is a substantial expansion magnification of the elastic member.