Abstract: A method of manufacturing an air permeable electrocast shell comprising forming a conductive layer on the surface of a model, placing a layer of elutable particles into close contact with the surface of the conductive layer and effecting an electrocasting treatment to deposit metal between the conductive layer and the particles, except for the points of contact between the conductive layer and the particles, and between adjoining particles. The deposit of the metal is controlled so that the thickness of the electrocast shell is less than that of the particle layer. Thereafter, the particles are eluted from the electrocast shell to form innumberable fine vent holes which open at both surfaces of the electrocast shell.