The present invention relates to a spacer for a prefabricated spiral staircase, which allows adjustment of a height of a gap between footboards for a prefabricated spiral staircase in multiple steps by using minimal disks, and a prefabricated spiral staircase using the same. The spacer for a prefabricated spiral staircase comprises a cylindrical pipe, a lower cap or upper cap, a disk, a height adjustment member, and a location determining member, wherein the height of the spacer is adjusted in multiple stages according to relative rotation between the upper cap and the disk or between the lower cap and the disk.