To improve the mechanical strength of a sheet and realize a lightweight and low cost sheet while its flexibility is retained by a method wherein a polyolefin- based foamed sheet and a meshed body, as the warps and woofs of which a composite thread consisting of a plurality of components having the melting points different from each other, are laminated to each other so as to heat-fuse the low melting point component of the composite thread and the foamed sheet together.

A composite thread 3 used as a reinforcing material is comprised of two kinds or more of thermoplastic resins having the melting points different from each other. As the thermoplastic resin, a polyolefin, the adhesion properties between a polyolefin-based foamed sheet and which is excellent, is preferable. When the difference between the melting point of a high melting point component and that of a low melting point component is 10°C or higher, the heat fusing work between the composite thread 3 and the foamed polyolefin sheet 1 can be stably performed, resulting in strongly integrating with the foamed polyolefin sheet. As the high melting point component, high density polyethylene, medium density polyethylene, straight-chained low-density polyethylene, polypropylene or the like, each of which is crystalline polyolefin and can obtain a high tenacity by stretching.