PURPOSE: To enable work of lifting and moving a manhole cover by a single tool by providing a supporting part for turnably and tiltably supporting an arm in the vicinity of a point end of the arm provided with an engaging part, engaged with a tool inserting hole of the manhole cover, in the point end.

CONSTITUTION: In an oil tank buried in a gasoline station or the like, a manhole covered with a cover 9 is provided for inspection. In the case of removing this manhole cover 9, first a T-shaped engaging part 8 in the point end of an arm 1 of an opening/closing tool is inserted from an about 90° direction against a long hole of a tool inserting hole of the manhole cover 9, and next by turning the arm 1 about 90°, the engaging part 8 is engaged with the tool inserting hole. Under this condition, next by pressing down a base end of the arm l, the cover 9 is vertically lifted by the action of levers. In this condition, by swinging the arm 1 rightward or leftward with a rotary block 4, supported onto a base seat 2 through a bearing 3, serving as the center, the cover 9 is moved sideward of the manhole and landed.