The invention relates to a material separation device, aims to solve the problem of analyzing impurity content in sodium-potassium alloy through a vacuum distillation mode and provides a sodium-potassium alloy vacuum distillation device. The sodium-potassium alloy vacuum distillation device comprises a distillation still, a crucible, a collecting tank, a refrigeration device and a vacuum unit, wherein a heating device is arranged at the outer part of the distillation still; the collecting tank is a sealed tank body; the middle part of the collecting tank is communicated with the top part of the distillation still through a pipeline; an inner cooler and an outer cooler are arranged in the collecting tank and both connected with the refrigeration device through a coolant pipeline; and the top part of the collecting tank is connected with the vacuum unit. The sodium-potassium alloy vacuum distillation device has a simpler structure, does not have the backflow phenomenon in the distillation process, has the advantages of small sampling quantity, good separation effect of the sodium-potassium alloy, serving as a matrix, high reliability, convenience, rapidness and safety in operation, economy, practicability and the like and better solves the vacuum distillation problem of the sodium-potassium alloy.