To provide a track expansion device for a magnetic levitated ground transportation system capable of keeping intervals of the track rail joints short even if the interval between the girders greatly change by the girders expanding or contracting.

A track rail of 10 m is used. A connecting means 6 of the joint of girders 2, 3 within ±20 mm regulates the detached distance and the approached distance to 20±20 mm. A sleeper 5 of the joint of girders 2, 3 within ±20 m is supported by a sliding means 11 in a movable manner in the longitudinal direction. Even if a great change takes place in the joint of girders 2, 3, such change is dispersed to respective joints of a track rail 4 within the joint of ±20 m. Thus joint intervals of the track rail 4 can be kept short.