A turning device that rotates a rotor of a turbine comprising: a pinion having spur teeth that mesh with a wheel gear provided on a rotary shaft , wherein a center of the pinion is formed with a through hole ; a pinion shaft which is inserted into the through hole , and which rotatably supports the pinion ; a pair of arms including a first end , a second end and a central portion , and configured to support the pinion at the first end via the pinion shaft ; a casing (C) which accommodates the pinion , the pinion shaft and the pair of arms ; an arm tilt shaft that is provided with the central portion of the pair of arms and rotatably supports the pair of arms on the casing (C); an operating rod , that extends in a vertical direction and is capable of moving in the vertical direction, a lower end portion of the operating rod being engaged with the second end of the pair of arms ; and an ON/OFF mechanism engaged with the operating rod via a tilting rod and configured to operate the pair of arms by moving the operating rod along the vertical direction, such that the pinion is brought close to the wheel gear, in a meshed position, with respect to the wheel gear and such that the pinion is separated radially outward from the wheel gear , in a retracted position; characterized in that the pinion is formed with concave portions at both side surfaces of the pinion in a direction of the pinion shaft , each of the concave portions surrounds the through hole ; thrust bearings are fitted in the concave portions ; and in the direction of the pinion shaft , a width of the thrust bearings is larger than a width of the concave portions . a pinion having spur teeth that mesh with a wheel gear provided on a rotary shaft , wherein a center of the pinion is formed with a through hole ; a pinion shaft which is inserted into the through hole , and which rotatably supports the pinion ; a pair of arms including a first end , a second end and a central portion , and configured to support the pinion at the first end via the pinion shaft ; a casing (C) which accommodates the pinion , the pinion shaft and the pair of arms ; an arm tilt shaft that is provided with the central portion of the pair of arms and rotatably supports the pair of arms on the casing (C); an operating rod , that extends in a vertical direction and is capable of moving in the vertical direction, a lower end portion of the operating rod being engaged with the second end of the pair of arms ; and an ON/OFF mechanism engaged with the operating rod via a tilting rod and configured to operate the pair of arms by moving the operating rod along the vertical direction, such that the pinion is brought close to the wheel gear, in a meshed position, with respect to the wheel gear and such that the pinion is separated radially outward from the wheel gear , in a retracted position; characterized in that the pinion is formed with concave portions at both side surfaces of the pinion in a direction of the pinion shaft , each of the concave portions surrounds the through hole ; thrust bearings are fitted in the concave portions ; and in the direction of the pinion shaft , a width of the thrust bearings is larger than a width of the concave portions . <EOS>