A separation membrane module may decrease a bending load applied to a support member supporting ends of tubular separation membranes and omission of a seal member between the outer circumferential surface of the support member and the inner circumferential surface of a housing. The separation membrane module may include a tubular housing, tubular separation membranes arranged in a longitudinal direction of the housing, end tubes connected to lower ends of the tubular separation membranes, a support box supporting the end tubes, and a backpressure chamber below the support box. The tubular separation membranes may be in communication with a support box collection chamber. A nozzle disposed on the support box may extract permeated fluid. A chamber and the backpressure chamber are in communication via a gap between the support box outer circumferential surface and the inner circumferential surface. The chamber and backpressure chamber have substantially the same pressure.