Discussed is a device for self-assembling semiconductor light-emitting diodes for placing the semiconductor light-emitting diodes at predetermined positions on a substrate by using an electric field and a magnetic field, the substrate being accommodated in an assembly chamber accommodating a fluid, the device including a substrate chuck configured to dispose the substrate at an assembly position, wherein the substrate chuck includes a substrate support part configured to support the substrate on which an assembly electrode is formed, a rotating part configured to support the substrate support part, and a controller configured to control driving of the substrate chuck, wherein the substrate support part includes micro-holes for injecting a gas between the fluid and the substrate, and wherein the controller controls whether the gas is injected through the micro-holes according to whether the substrate is raised or lowered.