كتب : Hatem Maher
The Argentinean striker scored the winner in the 58th minute when he capitalized on a poor marking by Carles Puyol and terrible positioning by keeper Victor Valdes to convert home Andres D'Alessandro's low cross.
Milito is now joint top scorer in the Primera Liga along with Sevilla's Malian striker Frederic Kanoute with 19 goals.
Icelandic striker Eidur Gudjohnsen and Argentinean prodigy Lionel Messi had a double opportunity to level the score but failed to deliver from close range.
Catalan giants Barcelona are on top of the league table with 56 points, two ahead of second-placed Sevilla who face Racing Santander on Sunday while Zaragoza lie fourth on 50 points.
Elsewhere, Valencia's title hopes suffered a setback after they were handed a stunning 1-0 defeat at Athletic Bilbao.
Igor Gabilondo netted what proved to be the winner in the 28th minute.
The defeat put Valencia in fifth place with 50 points, behind Zaragoza on goal difference as they risk losing the last UEFA Champions League spot.