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 with their respective permeate surfaces in opposition to each other and sealing the edges of the pair of the separation-membranes ; 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 through the through holes, - both ends of the shaft 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 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 . - 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 with their respective permeate surfaces in opposition to each other and sealing the edges of the pair of the separation-membranes ; 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 through the through holes, - both ends of the shaft 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 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 . <EOS>