PURPOSE: To measure static unbalance amount in high-precise, by finding the mean value of an unbalance amount obtained when a known turning torque is applied in a certain direction to an object to be measured and the unbalance amount obtained when it is applied in a reverse direction.

CONSTITUTION: A known turning torque is applied in a clockwise direction to an object to be measured pivotably supported, and when an angle, by which the object to be measured is turned by an additional torque, enters an angle range previously set and is balanced with it, a first static unbalance amount is computed from the first displacement angle and the addition torque. Then, a torque equivalent to a turning torque applied at the last moment of a preceding stage is applied in a counterclockwise direction and a second displacement angle to a position allowing them to balance with each other is measured to compute a second static unbalance amount. The first and the second static unbalance amounts are averaged, and the mean value is decided as the static unbalance amount o the object to be measured.