The present disclosure provides a locking structure of a valve timing adjustment apparatus for an internal combustion engine, using torque from a camshaft and the pressure of working fluid. The locking structure includes an anti-rotation mechanism for inhibiting or preventing a position change between a rotor and a housing by preventing relative rotation of the rotor to the housing. The anti-rotation mechanism further includes: a plurality of locking grooves which are formed on the ratchet plate with different depths and connected to each other; and a locking pin member. In particular, the locking pin member has: a hollow outer pin elastically disposed in a fitting hole formed in vanes, an inner pin elastically disposed inside the outer pin, and a lifter ring coupled to the upper portion of the outer pin to slide on the inner side of the fitting hole.