SEPARATION MEMBRANE ELEMENT

The present invention addresses the problem of providing a separation membrane element with which it is possible to stabilize the separation removal performance when a separation membrane element is operated. The present invention is a separation membrane element provided at least with a collecting pipe, a separation membrane, a feed-side channel material, and a permeation-side channel material, wherein: the feed-side channel material is configured from a fibrous column X configured from a plurality of fibrous materials A arranged in one direction and a fibrous column Y configured from a plurality of fibrous materials B arranged in a different direction to the fibrous column X; the fibrous materials A intersect the fibrous materials B to form intersections; and the fibrous materials A and/or the fibrous materials B have a small-diameter part and a large-diameter part between adjacent intersections in a section plane parallel to the respective fibrous column.