To shorten a positioning time, by preventing a suspended unit from being inclined to facilitate positioning of the center of gravity of a crane.

This crane 2 lifts a metal mold 1 as the suspended unit up/down suspended to travel, a plurality of lines 13 are drawn in an upper surface of the metal mold 1 to pass through its center of gravity, an optical pointer 4 is arranged in a position corresponding to a plurality of the lines 13 drawn in the upper surface of the metal mold 1 in a lower part of the crane 2, by controlling a position of the crane 2 so as to conform an irradiation beam from the optical pointer 4 onto a plurality of the lines 13 drawn in the upper surface of the metal mold 1, this positioning device for the center of gravity of the crane is controlled so as to conform the center of gravity of the metal mold 1 to the crane 2.