An object is to provide a main tower of a bridge having a rectangle-shaped cross section which can effectively reduce oscillation for wind blowing in the direction normal to the bridge axis. A cross sectional shape of a tower column is a rectangle shape with a direction normal to the bridge axis dimension smaller than a bridge-axis direction dimension. A slit passing through in the direction normal to the bridge axis is formed in a substantially central position, and a ratio of the bridge-axis direction dimension of the slit with respect to the bridge-axis direction dimension of the cross section is between 0.2 and 0.3.