To provide an auxiliary tool for a piping supporting tool which prevents bolts from falling before screwing nuts, which prevents the bolts from co-rotating with the rotation of the nuts when screwing the nuts, and the manufacturing cost of which is suppressed.

A co-rotation and coming-off preventing auxiliary tool 1 for bolts for the piping supporting tool has an auxiliary tool body which has holding parts 12, 12 that hold an installation piece of a piping supporting band 5 and which can slide along the installation piece. The auxiliary tool body also has through-holes, which extend in the sliding direction and in which wide width parts and narrow width ones are communicated with each other, and cut-and-raised parts, which make each of both opposite peripheral edges of the through-holes perpendicular to the sliding direction. The intervals of the cut-and-raised parts facing each other are the ones sandwiching the sides facing each other of the head of the bolts. The wide width parts of the through-holes are set at a size which allows the insertion of bolts that are inserted into the bolt insertion holes provided in the installation pieces of the piping supporting band, and the narrow width parts of the through-holes are set at the size which can lock the bolts.