To manufacture a concrete block which equips both water permeability, beautiful properties and furthermore intensive performance such as durability at a lower cost.

A plurality of pieces of projection parts are installed at prescribed intervals in the bottom 4a of a forming chamber 4. In this state, dense concrete is filled in the forming chamber so that a part on the upper end sides of the respective projection parts is left and these are buried and thereby a finished concrete layer 1A is formed. Furthermore, coarse concrete is filled on the upper face side of the finished concrete layer 1A and a part on the upper end sides of the projection parts is buried in the inside thereof and a water permeation concrete layer 1B is formed. Thereafter, the above-mentioned respective projection parts are removed and thereby drainage holes 2, 2... are formed in the removal traces. By such a manufacturing method as this, a concrete block, which consists of the vertical two layers of the finished concrete layer 1A and the water permeation concrete layer 1B and secures sufficient water permeability through the drainage holes 2, 2..., is easily obtained by simple work of beforehand arrangement of the respective projection parts and behindhand removal thereof without necessitating a large-scale device.