There are various facilities on the road and they are managed by installing the manhole cover at the entrance of the access hole, however, when a vehicle passes the manhole cover of which height does not match with the height of the road surface, there is a vehicle shock and uncomfortable vehicle ride due to a bump cause by the height differences. If the height and slope of the manhole cover presented on a road may have been adjusted in response to the road surface, it gives much help not only the improvement of ride comfort but also the prevention of a traffic accident which may occur from a sudden stop and low speed due to the bump. The present invention is not only capable of the height adjustment of the manhole cover but also able to adjust the road slope. It is also possible to reduce the raising cost of manhole cover when the height of the road surface is changed by a resurfacing of the road. It aims to reduce the cost of the height adjustment of the manhole as well as the convenience of construction in that new construction is simple and the height adjustment is possible frequently according to the local condition, even after a long period of time. It also has the merit of allowing the traffic for heavy vehicles immediately after securing the manhole cover.