In this study, a construction method which was able to reduce the differential column shortening of a tall building by using outriggers was proposed. By connecting the outrigger to the vertical members just after completion of the floor at which the outrigger is installed rather than after completion of the whole frame, the differential column shortening as well as the induced internal forces of the horizontal members were able to be reduced. Two plane frame models, constant section model and constant stress model, of 80-story reinforced concrete frame with shear wall were analyzed to study the effect of the location of the outrigger on the reduction of the differential column shortening. Optimum location of the outrigger can be determined by considering the reduction of the wind-induced lateral deflection and the reduction of the differential column shortening. Though additional internal forces were developed in the outrigger due to the early connection of the outrigger, the internal forces due to the differential shortening did not exceed the forces induced by the wind load.