PURPOSE: To detect a coordinate position with a high accuracy, by combining a substrate which has provided a light receiving element on the outside periphery, and a coordinate indicator for radiating a light beam at a prescribed angle.

CONSTITUTION: As for a light emitting element driving circuit 1 which has been connected to a coordinate indicator 11, light beams of (a)W(d) which have been emitted from a light emitting element 12 driven by an input signal (IS) of a switch, etc. which are not shown in the figure and have been reflected by a reflecting lens 14 are sent to light receiving elements 6a, 6b. In this case, (a) and (b) generate an electromotive force in A and B of the light receiving element 6a at an angle of θ1. In the same way, (c) and (d) also generate an electromotive force in C and D of the light receiving element 6b at an angle of θ2. It is inputted to a coordinate arithmetic circuit 4 through a comparator, a position of a coordinate indicator on a position detecting plate is calculated, and a coordinate position is outputted to an external equipment. As for the position, a circle C1 inscribed by a triangle in which the top and the base are an indicator E, and A and B, respectively, at the angle θ1, and a circle C2 inscribed by a triangle in which the top and the base are the indicator E, and C and D, respectively can be supposed. In this way, an intersection E of two circles corresponds to a position of the coordinate indicator. In this way, the coordinate position can be detected with a high accuracy.