Provided is a vapor phase epitaxy apparatus for a III nitride semiconductor, including a susceptor for holding a substrate, an opposite face of the susceptor, a heater for heating the substrate, a raw material gas-introducing portion provided at the central portion of the susceptor, and a reactor formed of a gap between the susceptor and the opposite face of the susceptor, in which a distance between the installed substrate and the opposite face of the susceptor is extremely narrow, and a constitution through which a coolant is flown is provided for the opposite face of the susceptor. The vapor phase epitaxy apparatus further includes, on the opposite face of the susceptor, a fine porous portion for ejecting an inert gas toward the inside of the reactor and a constitution for supplying the inert gas to the fine porous portion. The vapor phase epitaxy apparatus for a III nitride semiconductor is capable of efficient, high-quality crystal growth even when a crystal is grown on the surface of each of many large-aperture substrates held by a susceptor having a large diameter or even when a substrate is heated at a temperature of 1000° C. or higher before a crystal is grown.