PURPOSE: To form an in-mold foamed and molded body of a non-crosslinked linear polyethylene resin, by using as a base resin a linear polyethylene resin wherein the ratio of the weight-average molecular weight to the number-average molecular weight, the weight-average molecular weight, and the density are specified, and fulfilling a specific relationship between the density and the compression strength after the molding.

CONSTITUTION: As a base resin a linear polyethylene resin that has a molecular distribution wherein the ratio of the weight-average molecular weight Mw to the number- average molecular weight Mn measured by gelpermeation chromatography is 15 or over, a molecular weight Mw of 2×105 or over and a density D of 0.920g/cm3 or over is used. As the linear polyethylene resin is preferably used a homopolymer of ethylene such as a high-density polyethylene, a linear low-density polyethylene, etc. In the in-mold foamed and molded body, the density D(kg/m3) and the compression strength (the stress needed for compressing the molded body 2.5%) F(kg/cm3) should fulfill the given relationship wherein D is 15W100kg/m3. The foamed and molded body that fulfill such conditions is excellent in firm joining of the particles therein in spite of the fact that the in-mold foamed and molded body has been obtained from non-crosslinking polyethylene foamed particles.