To provide a three-dimensional meshing block which enables the free setting of the width of a fish pass for fishes, and simple work for reducing the influence of ocean waves when the block is immersed in the sea in construction work for installing the block in the sea or on the ground, which is prevented from being moved by a storm and an ocean current, which secures a stable matrix for algae, and which can be simply, efficiently and economically applied, for example, to the prevention of the displacement of the block for a retaining wall on the ground.

In a masonry structure, uneven surfaces with regularity in a unit of about a few centimeters, which can be vertically and mutually fitted into another block, are continuously arranged all over the top and bottom surfaces of the block; random masonry is adopted as a method for vertical masonry of the blocks; the upper and lower blocks are brought into close contact with each other and meshed with each other by the regularity and gravitation; and the way to horizontally lay and arrange the blocks is set to be a close contact type, or the width of a void space such as the fish pass is freely set at multiples of the width of the uneven surface in a unit of about a few centimeters, so that all the masonry blocks can be meshed with one another and three-dimensionally integrated together.