Munua initially joined Deportivo on a season-long loan last term from Nacional.
The 26-year-old has done enough to prove to Javier Irureta that he deserves a long-term deal at La Riazor.
Munua rarely figured last season with Spanish international Francisco Molina the first choice keeper at Deportivo.
Munua has signed a five-year deal at Depor and he will hope to see more action next season.
