A control device 200 calibrates a magnetic-field sensor 100 by computation. A computation unit 210 calculates the magnetic-field intensity based upon the outputs of X-axis, Y-axis, and Z-axis magnetic-field detection devices of the magnetic-field sensor 100. Such calculation is performed for four or more different points. The calculation is performed such that at least one point is not positioned on a plane including the other points. The computation unit 210 converts the outputs from the X-axis, Y-axis, and Z-axis magnetic-field detection devices of the magnetic-field sensor 100 into three-dimensional spatial coordinate points. Then, the computation unit 210 creates a sphere on which the four or more coordinate points thus obtained are positioned. The coordinate point of the center of the sphere thus created represents the magnetic-field offset. The interfering magnetic-field components in the X-axis, Y-axis, and Z-axis directions thus obtained are subtracted from the outputs of the X-axis, Y-axis, and Z-axis magnetic-field detection devices of the magnetic sensor 100, whereby calibration is made.