A valve opening/closing timing control device includes: a driving side rotator synchronously rotating with a crankshaft of an internal combustion engine; a driven side rotator coaxially disposed with a rotation axis of the driving side rotator and integrally rotating with a valve opening/closing camshaft; advance and retard chambers formed between the driving side and driven side rotators; a lock mechanism including a lock member capable of engaging with a recessed portion formed on one of the driving side and driven side rotators, and provided in the other of the driving side and driven side rotators; and a connecting bolt coaxially disposed with the rotation axis and connecting the driven side rotator to the camshaft, in which the connecting bolt includes an internal space, a valve unit accommodates a spool, and the spool includes an internal flow path, and, in the spool, a lock holding check valve is disposed.