When A denotes a required oil lower limit amount for one bearing near an oil supply source, and B and C respectively denote a required oil lower limit amount and a safety surplus oil amount for the other bearing away from the source, an amount of oil equal to A+B+C is supplied from the source and a hole diameter and the number of first oil holes are set such that an amount of oil to be supplied to the one bearing is equal to the amount A. Thus, the oil with the amount A can be securely supplied to the one bearing. Also, oil with the sum of the amounts B and C is supplied to the other bearing so that the oil with the amount B can be securely supplied to the other bearing which tends to receive oil insufficiently because of its remoteness from the source.