A gas injection apparatus, which can sequentially supply a substrate with at least two kinds of source gases reacting with each other in a container, and thin film deposition equipment including the gas injection apparatus, are provided. The gas injection apparatus includes a base plate, a first gas supply region protruding from the base plate, a second gas supply region protruding from the base plate and adjacent the first gas supply region, and a trench defined by a sidewall of the first gas supply region and a sidewall of the second gas supply region. The sidewall of the first gas supply region and the sidewall of the second gas supply region face each other and extend in a radial direction on the base plate.