A separation-membrane module, comprising: - an element block that is formed by arranging, in parallel, a plurality of separation-membrane elements that are formed by arranging a pair of separation-membranes (17, 24, 43, 51) with their respective permeate surfaces in opposition to each other and sealing the edges of the pair of the separation-membranes (17, 24, 43, 51); and - an aeration block that comprises an aeration pipe and that is disposed under the element block, wherein: - in the element block, at least one upper spacer is disposed in the upper portion of each space between the adjacent separation-membrane elements, and a lower spacer is disposed under the upper spacer in each space between the adjacent separation-membrane elements, - leftmost and rightmost separation-membrane elements of the plurality of the separation-membrane elements are secured to a frame only at the respective lower spacers, - the frame comprises a guide that is configured to limit horizontal movement of a portion of the leftmost and the rightmost separation-membrane elements of the plurality of the separation-membrane elements, the portion abutting the upper spacers, - each of the upper spacers, each of the lower spacers, and each of the separation-membrane elements have a through hole, - in the element block, the separation-membrane elements and the upper spacers, and the separation-membrane elements and the lower spacers are connected together by passing a shaft (10, 20) through the through holes, - both ends of the shaft (10, 20) that is passed through the lower spacers are secured to a housing frame with a fastener, - the leftmost and the rightmost separation-membrane elements are secured with a fastener near the both ends of the shaft (10, 20) that is passed through the upper spacers, and - the guide 14 is a channel that has a U shaped cross-section for receiving the end part of shaft (10, 20). - an element block that is formed by arranging, in parallel, a plurality of separation-membrane elements that are formed by arranging a pair of separation-membranes (17, 24, 43, 51) with their respective permeate surfaces in opposition to each other and sealing the edges of the pair of the separation-membranes (17, 24, 43, 51); and - an aeration block that comprises an aeration pipe and that is disposed under the element block, - in the element block, at least one upper spacer is disposed in the upper portion of each space between the adjacent separation-membrane elements, and a lower spacer is disposed under the upper spacer in each space between the adjacent separation-membrane elements, - leftmost and rightmost separation-membrane elements of the plurality of the separation-membrane elements are secured to a frame only at the respective lower spacers, - the frame comprises a guide that is configured to limit horizontal movement of a portion of the leftmost and the rightmost separation-membrane elements of the plurality of the separation-membrane elements, the portion abutting the upper spacers, - each of the upper spacers, each of the lower spacers, and each of the separation-membrane elements have a through hole, - in the element block, the separation-membrane elements and the upper spacers, and the separation-membrane elements and the lower spacers are connected together by passing a shaft (10, 20) through the through holes, - both ends of the shaft (10, 20) that is passed through the lower spacers are secured to a housing frame with a fastener, - the leftmost and the rightmost separation-membrane elements are secured with a fastener near the both ends of the shaft (10, 20) that is passed through the upper spacers, and - the guide 14 is a channel that has a U shaped cross-section for receiving the end part of shaft (10, 20).