Abstract: A support device for checking and repairing a heavy rotatable object such as a large turbine rotor comprises a pair of self-aligning support structures for rotatably supporting both ends of the shaft of the heavy rotatable object. In each self-aligning support structure, a roller support base rotatably supporting the corresponding end of the shaft of the object with a pair of support rollers is mounted on a base frame by means of a hemispherical support mechanism, and moreover a jig for adjusting the horizontal rotating position of the roller support base around the vertical axis of the hemispherical support mechanism is disposed in the periphery of the base frame, so that the occurrence of the thrust force on the heavy rotatable object as well as the support rollers is completely eliminated.