PURPOSE:To restrict an increasing of temperature in the bearing pockets by a method wherein low pressure fluid supplying means is arranged for fulfilling the discharging groove arranged between the bearing pockets with the low pressure and low temperature fluid. CONSTITUTION:A cooling pressurized fluid P2 is supplied to the discharging groove 8 arranged between the bearing pockets 7 through a radial passage 13 and then discharged to the annular discharging groove 24. Thus, the discharging groove 8 is always filled with a pressurized fluid of low pressure and low temperature and the pressurized fluid suctioned into the bearing pockets 7 from the discharging groove 8 under a rotation of the rotary shaft 5 is a cooled fluid to restrict an increasing of temperature in the bearing pockets 7.