A locking device comprising: a lock body; a plurality of dial rings; and a fixing member which is elongated in shape and is locked by being directly fixed with the plurality of dial rings, wherein said fixing member includes a convex-concave part with repeated concaves and convexes formed in the longitudinal direction of said fixing member, each of said dial rings includes a cutout which is provided on a part of the circumferential direction in such a manner that allows said fixing member to be freely inserted/withdrawn at a rotation position which is the unlocking position and that one of said dial ring abuts the convexes of the concave-convex part at a rotation position except for the unlocking position, said locking device includes a passage for inserting/withdrawing said fixing member, a part of the passage is a hole which reaches said dial rings from outside said locking device, and the hole is curved or flexed such that said dial rings are invisible from outside said locking device via the hole, and thus preventing the part for unlocking from being seen from outside the locking device.