To prevent the unsmoothing of rotational operations of operating members to the utmost, even on the occurrence of incompatibility between shaft portions of the inside and outside operating members.

In this structure of a long rod-like connecting shaft for the operating member, which passes through circular shaft holes of right and left side walls of a lock case, a fitting portion corresponding to an out-of-round portion-to-be-fitted of the operating member is formed at the base end of the connecting shaft; a first portion with a perfectly-circle cross section is provided in such a manner as to continue into the fitting portion; subsequently, an out-of-round engaging portion, which is engaged with a part of an inner surface of a through-hole of a cam member externally fitted to an approximately central portion of the connecting shaft provided in such a manner as to continue into the first portion, is formed; and after that, a second portion of the same shape as that of the first portion is provided in such a manner as to continue into the out-of-round engaging portion.