The highly-rated 19-year-old scored 18 times in 33 matches for the Catalan's B side last season and made a handful of substitute appearances for the senior side, resulting in him earning a long-term contract this summer.
Martinez has moved quickly to secure the teenager's services, making his fourth signing in three days after bring former Wigan players Arouna Kone and Antolin Alcaraz and Atletico Madrid goalkeeper Joel Robles, who was also at the DW Stadium last season, to Goodison Park.
"Gerard is a real diamond of Spanish football and a boy with incredible footballing talent and I am delighted that he has chosen to take the next step of his career with Everton," Martinez told evertonfc.com.
Deulofeu is a graduate of Barcelona's famed La Masia academy and has played for Spain's Under-17s, Under-19s, Under-20s and Under-21s.
He will join up with the Blues squad later this summer as he is currently on a break after involvement in the recent Under-20s World Cup in Turkey.