The utility model discloses a membrane distiller, belonging to the technical field of membrane separation devices. The membrane distiller comprises a rectangular case, an upper cover plate, a lower cover plate, a hollow fiber membrane assembly unit, a hollow pipe assembly unit, and a screen, wherein the upper cover plate and the lower cover plate are connected with the case, the hollow fiber membrane assembly unit is arranged in the shell, the screen is arranged between the hollow fiber membrane assembly unit, and the hollow pipe assembly unit, a feed liquid inlet and a feed liquid outlet are arranged on the cover plates, the cavity of the case has a three-section structure, the upper cavity and the lower cavity have a symmetrical two-cavity structure, at least two rows of hollow fiber membrane assembly units are fixedly arranged in the cavity at the same side of the upper cavity and the lower cavity through adhesives, at least two rows of hollow pipe assembly units are fixedly arranged in the cavity of the other same side of the upper cavity and the lower cavity, the upper cavity and the lower cavity are internally provided with a partition plate respectively, the partition plates are consistent in direction, the upper cavity and the lower cavity are single cavities which are communicated. The membrane distiller is simple in production process, mild in operation conditions, good in sealing effect, wide in application range, high in thermal efficiency, and capable of concentrating solution with high salt content, such as strong brine desalted from seawater.