Semi-permeable membrane support and method for producing semi-permeable membrane support

The present invention addresses the problem of providing: a semi-permeable membrane support which has few defects in a semi-permeable membrane and in which a semi-permeable membrane solution does not readily pass through the semi-permeable membrane and the semi-permeable membrane support, and which has improved membrane peel strength; or a semi-permeable membrane support which has few defects in a semi-permeable membrane and in which the salt rejection rate is improved. A semipermeable membrane support which is formed from a wet nonwoven fabric containing a main synthetic fiber and a binder synthetic fiber, and which is characterized in that: the fiber orientation strength of a coated surface on which a semipermeable membrane is provided is 1.00-1.30 inclusive, and the fiber orientation strength of a non-coated surface is 1.00-1.50 inclusive; the average surface area of the semipermeable membrane remaining on the coated surface of the semipermeable membrane support after the semipermeable membrane is peeled o