PURPOSE: To obtain a high-strength network web strong in one direction, by slitting an ultrahigh molecular weight polyolefin film in a specific state and stretching the slit film in the slitting direction, useful as various reinforcing materials for civil engineering, building, etc.

CONSTITUTION: This high-strength warp and weft laminate is obtained by making a large number of slits 13 extending in a zigzag way in an ultrahigh molecular weight polyolefin film 9 having ≥500,000 viscosity-average molecular weight by a slitter 11 so as to widen the film in a network state when the film is widened and stretching the film in the slitting direction. Film-forming properties and stretchability are improved by blending the polyolefin with a thermally flowing substance (glycerol, etc.) having ≤500,000 viscosity-average molecular weight and extrusion or co-extrusion.