A coordinate input apparatus detects a specified position in a coordinate-input effective area using a light projector that projects light onto a coordinate input surface and a plurality of light receptors that receive the light projected by the light projector. The coordinate input apparatus sets a first coordinate system based on a positional relationship between two light receptors constituting a first combination of the plurality of light receptors and a second coordinate system based on a positional relationship between two light receptors constituting a second combination that is different from the first combination, and converts a coordinate value of the specified position detected using the second coordinate system into a coordinate value in the first coordinate system.