To provide a method for separating oil and water with which it is possible to decrease the frequency of clogging in comparison with a method for separating oil and water using a filtration membrane.

This invention relates to a method for separating oil and water that is generated in the in-situ recovery method which produces bitumen 82 from oil sand layer 1500, the method conducting a step of preparing oil-containing water 83, 84 by taking out the bitumen 82 from bitumen-mixed fluid 81 that is recovered from the ground, and then subjecting the oil-containing water 84 to membrane distillation using a distillation membrane member 10 composed of a porous membrane.