Provided are a method of manufacturing a metal oxide and a substrate for a solar cell. The method of manufacturing the metal oxide according to the inventive concept includes mixing a metal precursor material, a basic material, amphiphilic molecules and distilled water to prepare a metal precursor solution, performing a first heat treatment with the metal precursor solution to form a metal oxide, and performing a second heat treatment with the metal oxide to form a pair of metal oxide disks having a single crystalline structure. A pair of zinc oxide disks includes a first disk, and a second disk separated from the first disk in a perpendicular direction to the first disk.