A manufacturing method for three-dimensional GaN epitaxial structure comprises a disposing step, in which a substrate of LiAlO2 and a source metal of Ga are disposed inside an vacuum chamber. An exposing step is importing N ions in plasma state and generated by a nitrogen source into the chamber. A heating step is heating up the source metal to generate Ga vapor. A growing step is forming a three-dimensional GaN epitaxial structure with hexagonal micropyramid or hexagonal rod having a broadened disk-like surface on the substrate by reaction between the Ga vapor and the plasma state of N ions.