To provide a method for producing a zeolite membrane composite body and a zeolite membrane composite body which can be used in operation for selectively separating olefin from an olefin/paraffin mixed fluid and has high separation performance.SOLUTION: In the method for producing the zeolite membrane composite body that film-forms an FAU type zeolite on a porous support, ion-exchanges cation that is ion-exchangeable in the FAU type zeolite with Ag ion by ion exchange, and produces a zeolite membrane composite body, an ion exchange temperature is set at a comparatively low temperature, and accordingly load on the FAU type zeolite is reduced, and a zeolite membrane composite body excellent in separation performance can be produced by preventing ion aggregation. The zeolite membrane composite body is excellent in olefin separation performance with a low olefin concentration of an olefin/paraffin mixed fluid, when olefin is selectively separated from the olefin/paraffin mixed fluid.SELECTED DRAWING: Figure 1