To provide construction machinery which can inexpensively recover energy along with the drive of a working element, while properly maintaining a weight balance and a balance of moment of inertia.

A wire rope 11 is stretched in an upper portion of an attachment 10. The wire rope 11 goes through pulleys 12a and 12b are arranged in the upper portion of a boom 4 and that of an arm 5, respectively; one end is connected to a joint 13 of a bucket cylinder 9; and the other end is connected to a drum of an electric motor 14 which is arranged in the rear of an upper vehicle body 3. The electric motor 14 enables both a regenerative operation and a power running one. When an operation command to perform the operation of lowering the boom 4, the operation of closing the arm 5 or the operation of closing a bucket 6 is input, the electric motor 14, which runs by the wire rope 11 unwound along with the motion of the boom 4, the arm 5 or the bucket 6, performs the regenerative operation and generates electric power.