To obtain a porous body capable of preventing stain characteristic of a porous body caused by rainwater, etc., various kinds of deteriorations by water of frost damage, etc., occurrence of efforescence and simultaneously preventing microorganism contaminations by algae and molds, making the best use of texture and color tone of material itself, having an excellent finish.

A permeable water absorption preventing material (2) mixed with an algae-proofing agent and a mildew-proofing agent is permeated into a porous substrate (1). The porous substrate (1) is coated with a film formation type water absorption preventing material (3) mixed with the algae-proofing agent and the mildew-proofing agent. Otherwise, the porous substrate (1) is mixed with an inner addition type water absorption preventing material (4) mixed with the algae-proofing agent and the mildew-proofing agent.