The invention relates to a method and arrangement for installing an elevator, which comprises an elevator car arranged to run in an elevator shaft along the guide rails, a balancing weight connected to the elevator car with suspension ropes and with a traction member, the elevator comprising further a hoisting machinery with a driving wheel in the lower part of the elevator shaft below the elevator car, the installing comprising one or more jumps to make the elevator serve higher floors. During the jump phase extensions needed for the suspension ropes are taken from first supply reels and extensions needed for the traction member are taken from second supply reels.