A lifting device includes: at least one first magnetic body, which is positioned on a platform and driven by a driving unit so as to move along a predetermined track; at least one second magnetic body, which is positioned above a part of track of the first magnetic body by a supporting device, and the magnetism of which is repulsive to that of the first magnetic body; and a lifting mechanism, which is fixedly connected to the second magnetic body, the second magnetic body is lifted or lowered according to the first magnetic body passing through or leaving from the second magnetic body during its movement course so as to cause the lifting mechanism to be lifted, lowered or swung. The lifting device can lift heavy objects by magnetic energy existing in the nature and has a simple structure, broad applicability, energy saving and high environmental protectionability. A power generation device and a sea reverse osmosis device that have the lifting device are disclosed.