The 54-year-old Spaniard was found to be paying two Moroccan labourers just €70 to work ten hours, six days a week, Spain's El Economista business paper reported on Tuesday.
That's just €1.17 an hour.
The joint operation involving Spanish police and Employment Ministry inspectors was launched after reports the businessman was abusing staff.
Inspectors found the two men were earning their pittance by carrying out tasks including bricklaying, gardening and moving furniture.
They were also be housed in conditions police described as "inhuman", without running water or a toilet.
Police said the men continued to work for the man to protect their only source of income. "Better here than parking cars," one of the men said.
Two Romanians who also worked for the Spanish man received a much higher income of €600 a month for just five hours work a day, six days a week.
Spain's legal minimum wage is €752.85 per month in 12 payments or €645.30 per month in 14 payments. This is €21 a day.
In October, the Spanish Government said it was looking at freezing the minimum wage in 2014.