PURPOSE: To reduce the weight of a railway rolling stock by contiguously arranging a rotor member and a stator member which are made of a carbon composite material in the inside space between a driving case having an istallation rotor key on an axle and a fixed case having an installation stator key on a shaft box and arranging a pressing means in the fixed case.

CONSTITUTION: A driving case part 5 which is freely fitted with an axle 3 is formed so as to be integrally rotatable with a wheel 2, and a fixed case part 7 extending to the vicinity of an axle rib part 2a from the outer peripheral part of a shaft box 4 is fitted with the shaft box 4, and the revolution is suppressed by a torque arm 26 engaged with a bogie frame. Rotor members 8,... and stator members 9,... which are made of the carbon group composite material in the inside space formed from the driving case 5 and the fixed case 7 are engaged with a rotor key 10 and a stator key 11 which are fixed with the driving case 5 and the fixed case 7. A pressing means 12 is installed on the fixed case 7. In brake application, each hydraulic pressure is supplied to pistons 13,..., and the rotor member 8 and stator member 9 are press- attached by a pressing plate 14. At this time, the brake torque is received by a bogie. When brake is not applied, the oil pressure is lowered, and the pressing plate 14 is returned by a slack adjustor 18.