The man, whose identity was not revealed, lives in Lloret de Mar, a seaside resort in northeastern Spain, and was taken on June 12 by people disguised as police, according to a statement.
He was released 11 days later after a police operation in Casarrubios del Monte, a small town close to Madrid where he was being held.
In their statement, police said his kidnappers had been lying in wait near his home.
They hit him, blindfolded him and forced into a car boot at gunpoint, he told police after his release.
A kidnapper then used the man's mobile to call his wife and demand a ransom of 1€.5 million ($1.7 million) in exchange for his freedom, police said.
During his detention, the hostage was constantly fed tranquilisers and sedatives by the alleged head of the gang, a Romanian man who studied medicine in Madrid.
Alerted by the victim's family, police tracked down the gang.
— Policía Nacional (@policia) July 3, 2017
They intervened just hours before a scheduled meeting to hand over the ransom at a hotel parking lot near a motorway.
Police said the kidnappers had started to take the hostage out — drugged and in a wheelchair — from where he was being held when they backtracked, presumably sensing they were being watched.
That's when police launched their assault, fearing for the hostage's life.
Five people have been detained.