To provide a method of purification reducing an amount of Cl which is an impurity in a gallium alkoxide useful as a raw material for forming a dielectric containing gallium oxide or a raw material for synthesizing a compound for photoelectron.

A gallium isopropoxide having 0.022 wt.% Cl content can be prepared with 89% yield by carrying out heat reflux of the gallium isopropoxide having 0.98 wt.% Cl content and potassium isopropoxide correspond to 1.4 times equivalent of Cl in toluene solvent for 5 h, then removing the solvent and singly distilling under vacuum.