To secure the degree of freedom of part layout around a swivel base by preventing a dead space from occurring on one side of the swivel base.

This crane comprises a cylinder support 5 so structured that a boom 2 can be liftably supported on the swivel base 1 through a hollow base pin 4 installed between the swivel base 1 and a boom foot part 2a and fitted sideways to the boss part 1a of the swivel base 1 and a double-acting cylinder 6 for attaching and detaching formed by disposing a cylinder part 8 in the hollow part 4a of the foot pin 4, connecting and fixing the cylinder part 8 to the foot pin 4, and connecting the rod end 7a of the cylinder part to a cylinder support 5. The cylinder 6 for attaching and detaching is structured by forming hydraulic ports 13, 14 for extension and retraction at the rod end 7a. The foot pin 4 can be extracted from the boom foot part 2a by retracting the cylinder 6 for attaching and detaching.

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