PURPOSE: To provide perfect balance by providing a turning arm with an upsetting moment removing weight pivoted along with the forward and backward movement of a head stock, a balancing weight suspending a saddle and the head stock with a chain and a hydraulic cylinder provided on a portion of the head stock suspending chain.

CONSTITUTION: A balancing device is constituted from a turning arm 15 with an upsetting moment removing weight 37 displaced by a hydraulic cylinder 38 pivoted along with the forward and backward movement of a head stock 13 supported by a saddle 12 moved vertically relative to a column 11, a balancing weight 16 suspending said saddle 12 and stock 13 respectively with chains 18, 20 trained over sprocket wheels 17, 17 and 19, 19 and having weight equal to sum weight of said saddle 12 and stock 13, the hydraulic cylinder 36 for locating a chain 20 suspending position at the center of gravity of the stock 13 and an unit for rotating a chain 34, sprocket wheels 33, 35, 35, a shaft 30, a pinion 32 and a segment 31 to turn synchronously the turning arm 15 along with the forward and backward movement of the stock 13. Thus, balance is kept even in the positional change of the saddle 12 and the stock 13 and change in the center of gravity when a working attachment is attached.