There is provided a balancing device for a four-cycle V-type eight-cylinder engine having a bank gap angle of 90 degrees, characterized by provision on a common rotating shaft (balance shafts 81, 82 as described in the mode for carrying out the invention) a part (an equivalent inertia mass P in the mode for carrying out the invention) for generating a first inertia force for offsetting a residual secondary inertia force from piston systems and a part (equivalent inertia masses VH, VV as described in the mode for carrying out the invention) for generating a second inertia force for offsetting a residual inertia force from valve systems. According to this construction, since balancing devices for piston and valve systems can be integrated into one unit, there is involved no complexity in construction.