Patent ID: 8303815

Claim:
A spiral-type separation membrane element in which a separation membrane, a feed-side flow passageway member, and a permeate-side flow passageway member are wound in a spiral form around a porous water-collecting tube in a laminated state, characterized in that said feed-side flow passageway member includes a first net-constituting thread in a direction tilted relative to a feed solution flow direction, the first net-constituting thread has a cross-sectional part such that a thread diameter in a direction parallel to a feed solution flow plane (X) is larger than a thread diameter in a direction perpendicular to the feed solution flow plane (Y), wherein the first net-constituting thread has a ratio (X/Y) within a range from 1.1 to 1.5, and a central part between intersection parts of the first net-constituting thread is made to have a thread diameter in a direction perpendicular to the feed solution flow plane (Y P1 ) smaller than a thread diameter in a direction perpendicular to the feed solution flow plane (Y P2 ) of an intersection part.