A traction drive is a device that transmits power between two rollers via lubricating oil. A traction drive is expected to be used for speed reducers for robot joint systems and automotive drive systems. However, cavitation occurs when the gas in the lubricant oil is being precipitated by the negative pressure in the rear vicinity of the contact part. The cavitation is considered to affect the flow of the rear part of an oil film and also causes various problems. Therefore, it is necessary to understand the characteristics of the cavitation in the traction drive. The operating environment of the high load and high peripheral velocity traction drive was reproduced, and the cavitation in the case of changing the load and the peripheral velocity was observed. Results confirmed that the cavitation expanded almost monotonously in the rolling direction up in low peripheral velocity condition, but tended to shrink as the peripheral velocity further increased. In addition, it was confirmed that the oil film was broken by connecting the atmosphere sucked from the rear part of the oil film and the cavitation.