A three-dimensional surface potential distribution measurement system for measuring a surface potential of a measurement object, the system comprising: a laser light source to emit laser light; a Pockels crystal having a first end surface and a second end surface, exhibiting Pockels effect in which a refractive index changes depending on potential difference between the first end surface and the second end surface, disposed such that the first end surface faces a side that the laser light emitted from the laser light source enters while the second end surface faces the measurement object, and extending in a longitudinal direction along a propagation direction of the laser light; a mirror disposed on the second end surface and configured to reflect the laser light incident from the first end surface of the Pockels crystal in a direction opposite to the laser light incident direction; a photodetector having a band following a high-frequency component of an inverter pulse voltage and configured to receive the laser light reflected by the mirror to detect a light intensity of the laser light corresponding to the potential difference between the first end surface and the second end surface of the Pockels crystal; and a housing configured to hold the laser light source, the Pockels crystal, the mirror, and the photodetector while maintaining a relative positional relationship thereamong, characterized in that the system further comprises a three-dimensional motion-driver capable of three-dimensionally moving the housing; and a driving controller configured to control the three-dimensional motion-driver, wherein the housing has a gap sensor configured to be moved integrally with the Pockels crystal and to measure a gap between the Pockels crystal and the surface of the measurement object, the driving controller is configured to control the three-dimensional motion-driver so as to make a gap signal output from the gap sensor become a predetermined value, and the driving controller is configured to control position and posture of the three-dimensional motion-driver such that the Pockels crystal faces a target portion of the measurement object with the gap having the predetermined value. a laser light source to emit laser light; a Pockels crystal having a first end surface and a second end surface, exhibiting Pockels effect in which a refractive index changes depending on potential difference between the first end surface and the second end surface, disposed such that the first end surface faces a side that the laser light emitted from the laser light source enters while the second end surface faces the measurement object, and extending in a longitudinal direction along a propagation direction of the laser light; a mirror disposed on the second end surface and configured to reflect the laser light incident from the first end surface of the Pockels crystal in a direction opposite to the laser light incident direction; a photodetector having a band following a high-frequency component of an inverter pulse voltage and configured to receive the laser light reflected by the mirror to detect a light intensity of the laser light corresponding to the potential difference between the first end surface and the second end surface of the Pockels crystal; and a housing configured to hold the laser light source, the Pockels crystal, the mirror, and the photodetector while maintaining a relative positional relationship thereamong, a photodetector having a band following a high-frequency component of an inverter pulse voltage and configured to receive the laser light reflected by the mirror to detect a light intensity of the laser light corresponding to the potential difference between the first end surface and the second end surface of the Pockels crystal; and a housing configured to hold the laser light source, the Pockels crystal, the mirror, and the photodetector while maintaining a relative positional relationship thereamong, the system further comprises a three-dimensional motion-driver capable of three-dimensionally moving the housing; and a driving controller configured to control the three-dimensional motion-driver, wherein the housing has a gap sensor configured to be moved integrally with the Pockels crystal and to measure a gap between the Pockels crystal and the surface of the measurement object, the driving controller is configured to control the three-dimensional motion-driver so as to make a gap signal output from the gap sensor become a predetermined value, and the driving controller is configured to control position and posture of the three-dimensional motion-driver such that the Pockels crystal faces a target portion of the measurement object with the gap having the predetermined value.