on this step the distribution of the load on the lifter is such that coupled with the ladder inclination the rear portion of the lifter is more heavily loaded than the front portion thereof enabling said floating up to be effected more smoothly as a result the clamping of the rails by the cams and arms is ensured further since the rows of brake cams and arms are disposed on both sides corresponding to the right and left rails the lifter can be floated up uniformly and symmetrically with respect to the right and left sides so that the stability is high further since the right and left cam shafts are separate from each other they can be securely and individually operated without being interfered with by each other further the cams and the upper surfaces of the rails are prevented from slipping relative to each other by the meshing between their irregularities and the lower surfaces of the rails and the arms are pressed against each other through the friction plates 19 so that there is no danger of slip occurring when the lifter is braked and stopped in addition thereafter the broken wire rope 7 will be pieced together or replaced by a new one when the ladder lies flat on the ladder truck there is no tension acting on the wire rope 7 so that brakage acts on the lifter during running of.