An apparatus is provided for depositing a thin film. The apparatus includes a chamber, a susceptor disposed in the chamber and supporting a substrate, a reflection housing disposed outside the chamber, a light source unit disposed in the reflection housing and irradiating light to the susceptor, and a light controlling unit blocking at least a portion of an irradiation path of the light to control an irradiation area of the light on the susceptor. At least a portion of the light controlling unit is disposed in the reflection housing.