A magnetic 3D-position/orientation measuring device measures the position of a receiver in a measurement space. A control device computes correspondence between a measurement space and a real space based on the measured value and a real-space value, which corresponds to the measured value and which indicates the position of the receiver in a real space. Also, the control device corrects an error of the measured value measured by the magnetic 3D-position/orientation measuring device based on the correspondence between the measurement space and the real space, the error resulting from the ambient environment.