Abstract: A novel tube or sheet-shaped fluid transmitting porous material containing as a substrate, a polyolefin. Such porous material can be readily produced by subjecting a mixture of a polyolefin, a specific secondary polymer and a decomposition type blowing agent to extrusion moulding. The present porous material has certain unique features in its structure characterized in that there are recurring communications between cell wall openings forming a passage through which a fluid can pass. This porous material has excellent gas and liquid transmitting properties as well as an excellent filtering property and, in addition, is superior in resistance to chemicals and also has mechanical strength. Therefore, the porous material according to this invention is widely applicable in agriculture and industry as well as in the fields of synthetic leather etc.