Laporte, still just 18, is now tied to the Basque club until June 2016 and has a buyout clause of 27.5 million inserted into his new deal.
The centre-back had already been handed a fresh contract until 2015, with a buyout clause of 18m, in December, but Athletic have rewarded him further for his continued development.
Laporte made his debut for the club in a Europa League tie against Hapoel Kirya in November and has since made six appearances in La Liga.
The defender is something of a rarity for Athletic in that he was born in France and captains their Under-19 side. However, he is eligible for the Basque-only club as he went to school in the region.
He started his youth career with Aviron Bayonnais - a team in France's Basque region that has an agreement to work with Athletic - and moved to the Liga club at the age of 16.