A report is made in the present paper of a series of tests that were conducted by devising a testing apparatus of a rolling cylindrical body. Special attention was paid to both the line contact and the point contact. It was planned to obtain quantitative information ragarding the chracteristics of friction in the rolling contact of the rolling body in the main shaft bearing of aircraft engines, as well as to measure its lifetime. The testing apparatus was designed on the following bases: (1) accurate measurement of the rolling frictional torque and (2) automatic detection of the lifetime of the rolling body by means of an oscillograph. In the present tests the slip ratio was nearly zero.The present tests were performed under static load, and under conditions of dry rolling, water lubrication and #60 spindle oil lubrication. The following conclusions have been obtained from the present tests.(1) From the tests of the line contact of the rolling cylindrical body under static load, the equipment has been found to be satisfactory for performing rolling fatigue tests, and specially for the automatic detection of the lifetime of the rolling body.(2) There are two inflexion points on the characteristic curve of the rolling friction coefficient, which are considered to show respectively the strength of the oil film and the rolling fatigue limit.(3) The three regions thus divided by these two inflexion points are respectively the region of rolling wear, the region of rolling fatigue damage and the region where remarkable evidence points to its complete freedom from rolling fatigue.