PURPOSE: To open/close a heavy manhole cover easily in order to make cleaning and inspection work in a manhole efficient.

CONSTITUTION: A pair of guide rails 2, 2 are disposed parallelly with a manhole cover 1 held in between, and moving bases 3, 3 are made travel on the respective guide rails 2, 2. A lift arm 5 liftable by a hydraulic jack 7 is placed on each moving base 3, and the front L-shape arm 6 of each lift arm is fastened to the cover 1. The lift arms 5, 5 are then elevated, and the moving bases 3, 3 are made travel at the same time to move the cover 1 easily into the opened/closed state.