PURPOSE: To obtain the title sheet excellent in the balance among physical properties by using a compatibilizer obtd. by the melt reaction of a mixture comprising a specific modified crystalline polyolefin or a specific hydrogenated block copolymer and a specific modified amorphous polyolefin.

CONSTITUTION: A compatibilizer is obtd. by the melt reaction of a mixture comprising 90-10wt.% modified crystalline polyolefin having carboxylic anhydride groups and/or carboxyl groups or 90-10wt.% carboxylic-anhydride modification of a hydrogenated block copolymer obtd. from an arom. vinyl compd. and a conjugated diene compd. and 10-90wt.% modified amorphous polyolefin having epoxy groups in the molecule. The title sheet is obtd. by compounding 0.1-10pts. wt. compatibilizer obtd. as above into 100pts.wt. mixture comprising an amorphous polyolefin having a heat distortion temp. of 100°C or lower and a high- density polyethylene.