Bubble-Bubble interaction in a free-rising bubbly flow is measured with three-dimensional Particle Tracking Velocimetry (3-D PTV). The present report mentions the dependency of the interaction pattern on Reynolds number of rising bubble from 5 to 75. With the measurement data, it has been newly found that high Re number bubbles had repulsive motion each other both in horizontal and vertical direction as the distance of bubbles was shortened. The technique of PTV for extracting accurately the 3-D velocity vectors of bubbles is also discussed.