A vapor phase epitaxial growth device comprises a reactor vessel. The device comprises a wafer holder arranged in the reactor vessel. The device comprises a first material gas supply pipe configured to supply first material gas to the reactor vessel. The device comprises a second material gas supply pipe configured to supply second material gas, which is to react with the first material gas, to the reactor vessel. The device comprises a particular gas supply pipe having a solid unit arranged on a supply passage. The device comprises a first heater unit configured to heat the solid unit to a predetermined temperature or higher. The solid unit comprises a mother region and a first region arranged continuously within the mother region. The mother region is a region that does not decompose at the predetermined temperature. The first region is a region that decomposes at the predetermined temperature and contains Mg.