Cavitation bubbles emit a very weak light due to bubble collapse. It is expected that the light emission may be closely related to cavitation erosion. In order to confirm the relationship between the erosion damage rate and the light intensity, experiments were performed for a water orifice cavitation flow. A circular pipe was used and water-cavitation generated around a column. For the measurement of light intensity, photon-counting method was used. And for visualization, the xenon gas-mixing method was adopted this by use of an image intensifier and chilled CCD camera. The damage rate was estimated by counting the number of damage pits. The light emission occurred around the end of cavitation, but the emission pattern was very different from the shape of the cavitation. The profile of the damage area was very similar to the light emission pattern and the maximum damage rate had a strong relationship with the maximum emission intensity.