The Partenopei received the penalty as well as bans for Paolo Cannavaro and Gianluca Grava following the club’s part in the scandal.
“I am undoubtedly very happy. This is not just a victory for Napoli, but for all of Italian football and for justice,” he told Sky Sport Italia.
“I believed and continue to believe in justice. I thank the judges who listened to us and debated for many hours. At the end of the day, innocence makes justice great. It was a right and equal sentence.”
Previously banned pair Cannavaro and Grava are now available for team selection again following a month of watching from the stands.
The decision also sees Napoli move up to joint-second in Serie A, only three points adrift of league leaders Juventus and the 63-year-old revealed he never gave up hope of overturning the ruling.
“In my mind we always did have that position with the points that we earned on the pitch," he added.
"The sporting justice system is making giant steps forward, but still needs to adapt to the times. I am happy for Grava, Cannavaro and all the fans, as nobody deserved this infamy.
De Laurentiis then expressed his hope that star striker Edinson Cavani will now remain in Naples and "become a symbol to identify the club", before coach Walter Mazzarri issued his relief at welcoming back two of his squad after a difficult festive period.
“First of all, I am very happy for Paolo and Gianluca, who are two lads with exceptional values,” he told the official club website.
“They had a terrible Christmas and were the victims of huge injustice. Naturally, I am also happy with our position in the table."