PURPOSE: To provide a device for stably and continuously forming a high- performance homogeneous LB film with the surface pressure and water level stabilized.

CONSTITUTION: A passage 10 holding a water phase to generate a stationary flow is formed by a developing region S provided with a means 19 for supplying a film material to the water phase 13 and developing the material, a compressing region C for forming a monomolecular film 12 from the molecule 11 of the material on the water phase 13 surface and with the water surface having a descent and a laminating region D for continuously depositing the film 12 on the surface of a substrate 15, and a separating region DS having a larger incliniation than the descent of the region C is formed at the boundary between the regions S and C. Accordingly, the interference between a feedback loop to hold the surface pressure of the monomolecular film 12 formed on the water phase 13 at a desired value by controlling the developing speed of the film material to be supplied in the developing region and a feedback loop to hold the water level constant in the laminating region by controlling the amt. of water flowing in and out of the device is reduced.