Fixed Motion Capture systems (Mocap) are well-established nowadays and are available in indoor and outdoor environments. Here, we introduce RobCap, a Moving Motion Capture System designed for acquiring accurate three-dimensional kinematics of human motion with large displacements. RobCap consists of an optoelectronic Mocap (Codamotion) mounted on a robotic arm, to track the human motion in the local moving frame. This paper presents this device and expresses the local kinematics of the markers in a global coordinate system. We have acquired a set of 560 measurements, by controlling the Robotic arm to follow the subject’s movement and to track the markers attached to his wrist. The performance of the RobCap is evaluated through comparison with state-of-the-art technologies. The 3D error is found to be ${9.7}\pm {4.1}\;\textit {mm}$ and ${3.9}\pm {0.8}\;\textit {mm}$ , respectively without and with calibration. RobCap increases the nominal capture volume of the fixed Mocap from ${75}\;{m}^{{3}}$ to ${523}\;{m}^{{3}}$ and the operational volume from ${105}\;{m}^{{3}}$ to ${1436}\;{m}^{{3}}$ . Our findings show that the RobCap is accurate and precise enough to be used as a mobile Mocap system for large displacements.