To provide a composite semipermeable membrane which has a high desalination rate and high water permeability even when surfactant-containing water is treated, and has a low deterioration rate of the water permeability.

This separation membrane for waste water treatment is used for treating the surfactant-containing water. A separation-functional layer of cross-linked polyamide is formed on a porous supporting membrane. The cross-linked polyamide contains an aromatic amine component and a straight-chained aliphatic amine component as polyfunctional amine components. The straight-chained aliphatic amine component accounts for ≥10% and ≤50% of the polyfunctional amine components by weight.