Left Luggage only at Barcelona & Madrid Airport

There are only 2 airports that have left luggage service in Spain.

Madrid Airport and Barcelona Airport

This is information from Madrid Airport
There are three left-luggage offices at the airport: the first in T1, the second in T2 and the third in T4. All baggage left at the left-luggage office passes through an x-ray checkpoint to verify that they do not contain dangerous items or objects.

This is information from Barcelona Airport
There is a left luggage office in the lobby of terminal B, beside the arrivals area. The price for all or part of each 24-hour period is €4.60 for a large locker, €4,10 for a medium locker and €3.60 for a small locker. Transfer from the left luggage office to the warehouse costs €37.08 and storage in the warehouse costs €1.85 a day.