Three-dimensional measurement capable of reducing an error in coupling robot and sensor coordinate systems and adverse effects of backlash in a robot. A position/orientation of the robot for obtaining a measurement value on the sensor coordinate system is set beforehand with a workpiece positioned at a reference position. Then, the robot is moved to a preparatory measurement position, a preparatory measurement for the workpiece positioned at an arbitrary position is performed (SV1), and based on a measurement result, a main measurement position is calculated (SV2). Next, an auxiliary position is determined (SV3), which serves as a start position from which a movement to the main measurement position can be made without making a reversal of respective axes. The robot is moved to the auxiliary position (SV4), and to the main measurement position (SV5), and a measurement for the workpiece is made and a measurement result is stored (SV6).