PURPOSE: To break tidal waves by receiving moderated movement of the side waves by a method in which the upper part of a breakwater plate is hung down from a concrete block having a waterway on its upper part and also a pump to suck up water into the waterway as the breakwater plate is moved by the side waves is provided.

CONSTITUTION: When receiving the side waves from the direction of X, a breakwater plate is pushed and retracted at a knob 7 as the center, a stop cock 13 is put into a cylinder 14, a valve 15 is closed and a valve 16 is opened, and the sea water is pushed up to a waterway 1 on the upper part of a block through a conduit 18. Also, when the side waves retreat, the stop cock 13 is also returned as the breakwater plate 6 returns, the valve 16 is closed and the valve 15 is opened, and the seawater is charged into the cylinder 14. Thus, the energy of the waves is consumed as a force of pushing up the seawater, the tidal waves are broken, and at the same time power generation is also attained by utilizing the seawater in the waterway 1.