Discussed are a device for self-assembling semiconductor light-emitting diodes, in which the device includes an assembly chamber having a space for accommodating a fluid; a magnetic field forming part having at least one magnet for applying a magnetic force to the semiconductor light-emitting diodes dispersed in the fluid and a moving part for changing positions of the at least one magnet so that the semiconductor light-emitting diodes move in the fluid; and a substrate chuck having a substrate support part configured to support a substrate, and a vertical moving part for lowering the substrate so that one surface of the substrate is in contact with the fluid in a state in which the substrate is supported by the substrate support part, wherein the vertical moving part provided at the substrate chuck lowers the substrate on to the fluid so that a force of buoyancy by the fluid is applied to the substrate.