Eighteen people were charged, most of them with links to Osasuna, including former president Miguel Archanco. The charges include fraud and sports corruption.
Appeals can be filed.
The two-year investigation probed 29 people, with 11 being cleared by judge Fermin Otamendi Zozaya, including current Osasuna coach Petar Vasiljevic, a former player.
The judge said Osasuna directors "decided to use money from Club Atletico Osasuna to keep the club at all costs in the first division of the Spanish league, delivering different quantities of cash to players from other teams with the intent of altering the result of the competition."
The money was allegedly paid in installments of 400,000 euros ($422,000) and 250,000 euros ($264,000) after a deal sealed at a hotel in Madrid in a meeting between Osasuna directors and two of the Betis players.
The 400,000 euros were allegedly delivered in cash in Seville, where Betis is based, by Osasuna directors Luis Vizcay Ventura and Jesus Peralta Gracia. The delivery supposedly happened two days before the game against Real Betis. The 250,000 euros were delivered in Madrid a few days after Osasuna's victory.
The judge said the money came from an account from Osasuna with the approval of Archanco and vice president Juan Antonio Pascual Leache.
Osasuna was not able to escape relegation because it also needed Almeria to lose its home match against Athletic Bilbao. It ended 0-0.
The judge said the investigation also showed that the Betis players allegedly asked for more money afterward, but were denied because of the club's economic difficulties at the time.
The directors allegedly tried to cover up the traces of the payments by saying that the money was used in fees to two local real estate agents. The agents were also charged by the judge.
Osasuna returned to the top flight this season. It is in last place with only one victory after 22 matches. Betis, sitting in 13th place, spent only one season in the second division after the demotion in 2014. Valladolid remains in the second division, in ninth place.