To miniaturize an interlocking member and to improve its durability by obtaining the interlocking member for a lock mechanism improving strength in a force transmission structure degraded in strength by a request for thinning.

The interlocking member 100 for the lock mechanism has a locking hole 37 for locking a claw plate 39 projected outward in the radial direction of an input shaft 41, on one end side, wherein the locking hole 37 is locked to the claw plate 39 and linearly moved to one end side by the rotation of the input shaft 41 to linearly move to the one end side a sliding member 11 of the lock mechanism 11 engaged with a protruding body 35 protrusively provided on the other end side. The interlocking member 100 is provided with a first driving plate 49 on the one end side formed of a stainless steel material and having the locking hole 37, and a second driving plate 51 on the other end side formed by die casting and having the protruding body 35. The other end 49a of the first driving plate 49 and one end 51a of the second driving plate 51 are superimposed, and the overlapped ends 49a, 51a are fixed by a plurality of fastening means 53 for fastening in an overlapping direction.