Residence and work permits are being given to unregistered immigrants, who can prove they have lived in Spain for at least six months and can show a contract from an employer offering them work for the same length of time.
"So far, we have 672,347 jobs emerging from the underground economy," Labour Minister Jesus Caldera told reporters on Saturday, the last day to apply for amnesty in Spain.
According to the latest data from municipal records, there are about 1.4 million undocumented or illegal immigrants currently living in the country.
The Spanish government expects to grant another 400,000 permits to children and close relatives of undocumented workers joining the amnesty, Minister Caldera said during a visit to one of the social security offices.
The amnesty for illegal immigrants is expected to have a significant impact on the country's social security system, increasing the number of registered workers by about 4%.
Undocumented workers from Ecuador led the amnesty pool with more than 21% of total applications, followed by immigrants from Romania, Morocco and Colombia, according to official statistics.
More than 42% of total applicants were female workers.
Spain has implemented six amnesty programmes in the past 15 years, with the number of legal immigrants quadrupling to more than two million at present.
But as the Spanish economy boomed in recent years, illegal immigration flows have persisted.