PURPOSE: To adjust the sag of a multiconductor power-transmission line without removing a spacer by providing a sag adjusting tool between an distance holding piece and a steel tower for power-transmission line and collectively moving conductors through the distance holding piece.

CONSTITUTION: When unbalanced tension acts on one of the electric cables supported by a sag adjusting unit, distance holding plates 1a, 1b, 1c, and 1c turn around connecting points at the apex angles of the plates 1a, 1b, 1c, and 1d so as to balance the tension of each cable. When hydraulic cylinders 6a and 6b are driven, the movement of the electric cables can be made equal to each other and, even when a spacer S is provided to each electric cable, the spacers S are not damaged. At the time of adjusting the sag of an already laid power-transmission line, the sag adjusting work can be reduced remarkably, because it is not required to remove the spacers S.