The pullback, which comes several months earlier than planned, leaves Spanish troops only in western Herat province, Khaama Press reported Saturday.
The withdrawal from Qala-i-Naw had been scheduled for autumn. All Spanish troops are scheduled to out of Afghanistan in 2014.
Several units have already been deactivated and 45 soldiers are scheduled to return to Spain Tuesday, Spanish defense ministry officials said.
Spain had deployed about 1,400 troops as part of the NATO-led International Security Assistance Force in Afghanistan. About 100 Spanish military personnel have died in the conflict, most of them in air accidents.