A device for self-assembling semiconductor light-emitting diodes , comprising: an assembly chamber having a space for accommodating an assembly solution (F); a magnetic field forming part having a plurality of magnets for applying magnetic force to the semiconductor light-emitting diodes accommodated in the assembly chamber dispersed in the assembly solution (F), the magnetic field forming part includes at least a horizontal moving part for changing positions of the magnets with respect to the assembly chamber ; and characterised by a substrate chuck comprising: a substrate support part configured to support a substrate (S) having an assembly electrode , wherein the substrate support part includes first and second frames each including a hole (210"') formed therein, the first and second frames are configured to hold the substrate (S), and the hole formed in each of the first and second frames is disposed to be overlapped with an assembly surface of the substrate (S) when the substrate (S) is loaded into the substrate support part ; a vertical moving part for lowering at least parts of the substrate support part into the assembly chamber , and an electrode connection part for being connected to the assembly electrode of the substrate (S); and wherein the first frame comprises: a bottom portion at which the hole is formed; and a sidewall portion (210") formed at an edge of the bottom portion , a height of the sidewall portion (210") is greater than a depth at which the bottom portion of the first frame is submerged in the assembly solution (F). an assembly chamber having a space for accommodating an assembly solution (F); a magnetic field forming part having a plurality of magnets for applying magnetic force to the semiconductor light-emitting diodes accommodated in the assembly chamber dispersed in the assembly solution (F), the magnetic field forming part includes at least a horizontal moving part for changing positions of the magnets with respect to the assembly chamber ; and characterised by a substrate chuck comprising: a substrate support part configured to support a substrate (S) having an assembly electrode , wherein the substrate support part includes first and second frames each including a hole (210"') formed therein, the first and second frames are configured to hold the substrate (S), and the hole formed in each of the first and second frames is disposed to be overlapped with an assembly surface of the substrate (S) when the substrate (S) is loaded into the substrate support part ; a vertical moving part for lowering at least parts of the substrate support part into the assembly chamber , and an electrode connection part for being connected to the assembly electrode of the substrate (S); and a substrate support part configured to support a substrate (S) having an assembly electrode , wherein the substrate support part includes first and second frames each including a hole (210"') formed therein, the first and second frames are configured to hold the substrate (S), and the hole formed in each of the first and second frames is disposed to be overlapped with an assembly surface of the substrate (S) when the substrate (S) is loaded into the substrate support part ; a vertical moving part for lowering at least parts of the substrate support part into the assembly chamber , and an electrode connection part for being connected to the assembly electrode of the substrate (S); and a bottom portion at which the hole is formed; and a sidewall portion (210") formed at an edge of the bottom portion , a height of the sidewall portion (210") is greater than a depth at which the bottom portion of the first frame is submerged in the assembly solution (F). <EOS>