PURPOSE: To improve the strength so as to spread a use by embedding a fiber yarn streak object, in which a coefficient of linear expansion and strength are specified, to be parallelly arranged in foaming styrene resin and forming a block for specifying its bending strength and compressive distortion factor.

CONSTITUTION: A fiber yarn streak object 2 of mechanical rollup shrinkage yarn and air finished yarn or the like with a coefficient of linear expansion (1 to 10)×10-5 while with strength 10 to 15kg/streak is provided and formed preferably in different shape. Next the yarn streak 2 is arranged with a space about 0.5 to 1cm and tightened by tensile force about 1 to 2kg/1,000den. Then in both sides of the yarn streak 2, foaming styrene resin 1 with a foam multiplying factor about 1 to 60 times and bending strength single about 2kg/cm2 or more is provided by heat foaming, and a block A with bending strength 6 to 15kg/cm2 and compressibility 4% or less is formed. In this way, the block can be easily manufactured while into light weight further with bending strength possible to improve by 2 to 4 times the conventional, and the block can be used for a structure.