The present invention provides a bilayer membrane produced using a microchannel capable of easily forming bilayer membranes such as planar lipid bilayer membranes in large quantities, and a production method thereof. A process for producing a bilayer membrane of the present invention comprises forming a state where two liquid phases or liquid and gaseous phases each containing amphipathic molecules are alternately arranged in a microchannel, discharging one of the two liquid phases or the gaseous phase of the liquid and gaseous phases through branch minichannels formed in the wall on one side or in the walls on both sides to contact the remaining liquid phases adjacent to each other, and thereby forming a side-by-side arrangement of bilayer membranes comprising the amphipathic molecules.