An overhead line tension balancer is configured so that an inner tube which is connected to an overhead line does not rotate, so that a rotation preventive function is not impaired even if the stroke of the overhead line is long, and so that the manufacturing step of the overhead line tension balancer is not complex. A retaining plate (113) is provided within an inner tube (108). The retaining plate (113) is provided with an opening through which a long plate (115) can move relative to the opening in a state in which the opening cannot rotate relative to the retaining plate (113) and in which the long plate (115) penetrates through the opening. The long plate (115) comprises two L-shaped long plate pieces having bent front ends. The bent portions serve as engagement sections (115a) which prevent the retaining plate (113) from coming off the long plate (115). The two long plate sections can individually engage with the retaining plate (113), and as a result, manufacturing is simplified.