To keep smoothness of an operation of an operation shaft even when the operation shaft independently inserted from the inside and outside of a room to a handle operation piece of a lock box is tilted.

A scoop prevention mechanism includes: a first operation shaft 3 whose inner end part is turned to a small diameter leaving an inner end of a handle shaft with an irregular shape cross section, which is rotatably supported by a handle shaft pedestal 2; and a second operation shaft 4 whose middle part is turned to the small diameter leaving irregular shape cross section parts at both ends. The inner end of the first operation shaft 3 and the outer end of the second operation shaft 4 are coaxially inserted to a coupler cylinder 5 of the irregular shape cross section, the first and second operation shafts are integrally connected by a first pin 6 which passes through the coupler cylinder 5 and the inner end of the first operation shaft 3 and a second pin 7 which passes through the coupler cylinder and the outer end of the second operation shaft and is orthogonal to the first pin, and the degree of the fitting is set so that the operation shaft and the pin passing through it can be mutually turned.