The three dogs repeatedly bit the man in the face and knees in Monday's horror attack in a park in the the town of Torrelaguna in Madrid province.
Ambulance workers said skin had been ripped from the man's face, jaw and scalp. He also had serious injuries to one knee.
The victim of the attack was rushed to Madrid's La Paz hospital in a serious condition, Spanish daily ABC reported.
Local authorities said the man attacked was a regular walker in the park. The dogs involved included two pit bull terriers and one dog of a race not described as dangerous.
Municipal police are now trying to track down the owner or owners of the dogs.