The Spaniard had to cope with tougher conditions on Friday's day two, as he made two birdies and a single bogey in a patient performance to reach 10 under par.
Italy's Renato Paratore was alone in second place on eight under after finishing his round with a hat-trick of birdies to sign for a second-successive 68.
New Zealand's Daniel Hillier was another shot back in third, one ahead of the group containing England's Marcus Armitage, Swede Marcus Kinhult and Spaniards Adrian Otaegui and Alejandro Del Rey.
After adding a 79 to his first-round 80, Blake Windred, the lone Australian representative, failed to make the cut, finishing last in the field alongside Spain's Angel Hidalgo at 15 over.
Campillo began the day with a three-stroke advantage following Thursday's 63 and still topped the leaderboard by the time he teed off in the afternoon.
After going close with lengthy putts at the opening three holes, Campillo opened his birdie account from five feet on the long fourth but gave the shot back at the next after failing to get up and down from a bunker.
Nine straight pars followed before his next birdie arrived at the 15th, where a wonderful approach shot set up a four-foot putt.
And he parred his way home to head into the clubhouse as the only man in double figures under par.
"I was trying to shoot under par," said Campillo.
"After a nine under, it's hard to play the day after so I was trying to have an under-par round after, which I did, so I'm quite happy with it."
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