The present invention relates to a building material design support system for supporting design of a building material capable of exhibiting a random texture pattern as a whole in a state in which the building materials are installed on a building portion and exhibiting continuity of the texture of adjacent building materials, such building material and a program for use in such building material design support system. More specifically, on a building material, first convex portions #A1L, #A1R, #A2L, #A2R to be arranged next to corresponding first convex portions of an adjacent building material have a prescribed texture common to every building materials, and the second convex portions have randomly arranged textures different from each other on every building material.