The number of people registered as unemployed hit 4.83 million in the month, a Labour Ministry report said, a peak unmatched since existing records began in 1996, and one of the highest levels in Europe.
Another 128'242 people joined the jobless queue in the month, pushing the total up 2.7 percent from September. Compared with a year earlier, the October figure was up by 472'595 people, or 10.84 percent.
It is the latest sign of a deep recession, which has gripped Spain's economy since mid-2011.
Prime Minister Mariano Rajoy says his labour reforms will turn the market around.
But in the meantime job seekers are in deep trouble, and analysts say a biting austerity programme aimed at saving 150 billion euros from 2012 to 2014 is delaying any exit from the recession. Public sector cuts, a post-summer slump and a permanent decline in construction were to blame for the bleak October jobs news, state secretary for social security Tomas Burgos said in a statement.
Spain is still suffering from the fallout after a 2008 property market crash, which threw millions out of work.
The October increase in job seekers was slightly more modest if the impact of seasonal blips is stripped out.
Seasonally adjusted data showed the number of registered unemployed rose by 21'210 from the previous month to 4.84 million in October.
A broader, quarterly household survey by the National Statistics Institute provides the official unemployment rate, which hit 25 percent in the third quarter for the first time in modern Spanish history.