A distance measuring device of camera for measuring distance to a pictured object includes pulse-driven first, second and third beam projecting elements. When a distance to the pictured object is long and beams of the beam projecting elements reflected from the pictured object are small in quantity or become nil, the first beam projecting element is pulse-driven until the number of light emission reaches a predetermined first maximum number of light emission, and the second and third beam projecting elements are pulse-driven until the number of light emission reaches a predetermined second maximum number of light emission which is less than the predetermined first maximum number of light emission. Because of this, when a distance to the pictured object is long and the beam projecting elements are pulse-driven to the predetermined first or second maximum number of light emission, it is possible to shorten a distance measuring time.