DERRICKING CRANE

PROBLEM TO BE SOLVED: To contrive moment balance without increasing the weight of a weight in a derricking jib crane in which moment balance is contrived by a counter weight. SOLUTION: This derricking jib crane is constituted by making a counter weight 12 movable so as to approach and separate from a base 2, providing a means calculating a balance location of a weight from lifting loads and a working radius of a jib 4 and providing a means moving the counter weight 12 based on the balance location of the weight calculated by the means when the derricking of the jib 4 is locked and loads are wound and lowered by operating a winch 5 for winding, separating slung load from the ground, gradually increasing loads in the slung load, grounding the slung load, gradually reducing loads in the slung load and obtaining moving time of the counter weight 12.