An image generating device for generating a depth map is provided. The image generating device includes an image sensor including phase detection pixels, a lens driver adjusting a position of a lens to adjust a distance between the lens and an object, a phase difference calculator calculating first phase differences based on first phase signals generated when the lens is placed in a first position and calculating second phase differences based on second phase signals generated when the lens is placed in a second position being different from the first position, and a depth map generator generating first and second depth data associated with a distance between the phase detection pixels and the object based on the first and second phase differences and generating a depth map based on the first and second depth data.