A separation membrane element of the present invention includes: a water collection tube; and a plurality of separation membrane leaves stacked on each other and wound around the water collection tube, each of the separation membrane leaves includes one or more separation membranes each having a feed-side face and a permeate-side face and is configured so that the feed-side faces face each other, and a sheet having a plurality of projections fixed thereto is provided between the permeate-side faces of the separation membrane leaves stacked on each other. Regarding a height of the projections, a ratio of the maximum height to the minimum height is from 1.10 to 1.50, and a variation coefficient of the height is from 0.02 to 0.15, and an impregnation ratio of the projections into the sheet is from 10% to 100%.