Damage in rolling contact fatigue was observed using polycarbonate which is a transparent material. The rolling contact fatigue tests were performed using a set of one polycarbonate and one carbon steel S45C rollers under lubricated condition. In the tests, damage occurred only in the polycarbonate. With the carbon steel was set as the drive side, experiments in which the rollers were rotated in a single direction and those in which the direction of rotation was changed at a frequency of every 3×105 times were carried out. In the former case, arrowhead shaped surface cracks were initiated, and pits were subsequently formed under the conditions of maximum principal stress criterion. In the latter case, pits were formed which appeared elliptic from a surface view. The cracks then grew from the pits bottom toward the center of roller. When the polycarbonate was set as the drive side, internal cracks initiated in shear mode, then the surface layer of the polycarbonate peeled off. From those experiments, it was found that damage mechanisms of rolling contact fatigue changed depending on the loading conditions. These mechanisms are influenced by the friction of the roller surfaces and the pressure of the oil which enters the cracks.