11 the member is formed to have a thickness of about 1 8 mm and a length of about 2000 mm which is the spacing of the h shaped steel 30 in addition the height is about 250 mm as shown in fig5 and 6 a sandwiching portion 13 is formed at both ends of the sound insulating member 11 this sandwiching portion 13 is formed by arranging a cutout portion 14 at both ends of the sound insulating member 11 in which cutout portion 14 is cutout by length l 1 so that the width w 1 of the sandwiching portion 13 is slightly smaller than the width w 2 between the flanges 31 31 of the h shaped steel 30 and to a width enabling the sandwiching portion 13 to be inserted between the flanges 31 31 of the h shaped steel 30 by this cutout portion 14 on the other hand the length l 2 in the long direction of the cutout portion 14 is set to a length that the sandwiching portion 13 can be attached to the flange 31 but a slight margin is desirably provided thus even if dimension error is produced in the spacing of the upstanding h shaped steels 30 30 the error can be absorbed thereby reliably attaching the sound insulating member 11 the sound insulating member 11 is positioned in the length direction after attachment by the cutout portion 14 and is prevented from oscillating with respect to the h shaped steel 30 the sound insulating member 11 configures a sound insulating wall 10 having an appropriate height by inserting and.