Abstract: A synchronous balance device to maintain a car body balanced without inclination due to eccentric force during turning, and to offset eccentric forces during turning, and to offset eccentric forces to increase safety. Two sets of two hydraulic cylinders are mounted on left and right sides between the car body and axle. An oil feed port on one left hydraulic cylinder communicates with an oil discharge port on a right hydraulic cylinder, and an oil discharge port on the other left hydraulic cylinder communicates with an oil feed port on the other right hydraulic cylinder. When the car body is inclined with one side rising and the other side sinking piston rods of the hydraulic cylinders on the rising side pull down the car body to keep it balanced. Therefore, the present invention enables a car body to keep from becoming inclined during turning so as to increase driving safety.