An underground structure cover comprises a cover body (10) and a receiving frame (20) arranged so that the cover body is fitted in and supported by the receiving frame in the manner that an inclined surface (11) of the outer circumference of the body meets an inclined surface (21) of the inner circumference of the frame. The inclined surfaces (11, 21) each have an upper inclined surface (11a, 21a) and a lower inclined surface (11b, 21b), and the lower inclined surfaces (11b, 21b) are steeper than the upper inclined surfaces (11a, 21a). The body (10) is fitted in and supported by the part (20) at the upper inclined surfaces (11a, 21a) and the lower inclined surfaces (11b, 21b). By this, the body is prevented from being wedged into the frame too deeply and also from becoming inclined with respect to the frame or riding up.