Coordinate detector and electronic information board system

A coordinate detector includes a pair of light sensor units disposed on a side of a display part having a display surface to be touched by a target to be detected, optical reflective members respectively disposed on remaining three sides of the display part, and a sensor position adjusting unit configured to adjust a rolling direction of the light sensor unit with respect to the optical reflective members. When the target touches the display surface, coordinates of the target are detected based on light reflected off the optical reflective members that is received by the light sensor units.