A guide wheel device for a guide rail vehicle includes a wheel shaft rotatably supported on a bearing, and a main guide wheel and a branch guide wheel rotatably mounted to upper and lower portions of the wheel shaft, wherein the main guide wheel has a rotation center eccentric to an axis of the wheel shaft, a plurality of fitting body receiving portions are provided in an outer peripheral surface of the wheel shaft so as to be arranged sequentially in a circumferential direction, a fitting body to be fitted into the fitting body receiving portions is provided in the bearing, and fitting adjusting means capable of pressing the fitting body against the fitting body receiving portions toward the wheel shaft or releasing the pressing of the fitting body is provided.