β-Ga 2 O 3 nanocolumns straightened and crossed perpendicularly each other were deposited on MgO (100) substrate by vapor phase transport method. Growth of the nanocolumns was examined at steps of 1000, 1050, and 1200°C in elevation of source-boat temperature. We have drawn out the substrate from deposition-tube at each source-boat temperatures of 1000, 1050, and 1200°C. Scanning electron microscopy of the sample with source-boat temperature of 1200°C demonstrated that the straightened and elongated nanocolumns are crossing perpendicularly each other. Typical lengths of the nanocolumns were in the range of several hundreds nanometers below 1050°C, and those of 1200°C were in the range of ten to fifteen hundreds nanometers. Diameters of the nanocolumns stayed in the range of few hundreds nanometers, notwithstanding variation of the source temperature. X-ray diffraction and transmission electron microscopy with energy dispersive X-ray spectroscopy revealed that the nanocolumns are monoclinic β-Ga 2 O 3 crystal, and the (400) plane of β-Ga 2 O 3 nanocolumns is parallel to the (100) plane of MgO substrate.