To provide an arrangement of a hydraulic piping within a mast with excellent visibility because the mounting of a hose pulley hinders a front visibility because the hose pulley is arranged at the inside of a rail of a mast device when the hydraulic piping for moving a working machine such as a side shift is conventionally increased and bad visibility becomes a problem for safety in works.

This piping within a mast is characterized by setting a gap dimension 4 held by front surfaces of an inner rail 1 and an outer rail 2 and a rear surface of a finger board 3 in the mast device to be slightly larger than a width dimension 6 of the hose pulley 5 and arranging the hose pulley 5 at an intermediate of the gap dimension 4.