It is an object of the present invention to provide a separation membrane in which a film-forming solution can be prevented from reaching a rear surface of a porous support in a step of forming a film, the adhesion between a functional film for separation and the porous support is high, and the thickness can be reduced. In the present invention, the separation membrane includes a porous support having a rough rear surface and a functional film for separation, and the functional film is disposed on a front surface of the porous support and extends into the porous support.