A position detector detecting an object's position includes: first, second and third light sources emitting first, second and third position detection light beams to form first, second and third intensity distributions in a detection area, a highest intensity portion of the second intensity distribution being shifted from that of the first intensity distribution, a highest intensity portion of the third intensity distribution being shifted from a straight line connecting the highest intensity portions of the first and second intensity distributions; a light detector detecting the first, second and third position detection light beams reflected by the object; and a position detection section detecting a two-dimensional coordinate of the object in a detection plane set in the detection area by comparing the intensities of the first and second position detection light beams, and comparing the intensities of the second and third position detection light beams.