<p>Since membrane elements are fixed at small intervals on the element block in a membrane separation device for treatment of sewage and waste water, the membrane elements adjacent to each other are collided with each other and worn by the vibration generated during the operation of the device. To overcome this problem, a central spacer part (41) with a through-hole (50) the thickness of which is equal to the interval between the membrane elements is provided on the upper edge or the lower edge of a support plate for supporting the membrane elements. When the membrane elements are stacked to form an element block, both ends of the membrane elements are fixed, and a shaft (54) for fixing is inserted into the through-hole (50) and pressingly fixed by a fastener (53).</p>
