The woman, in her 90s, was located by sniffer dogs on Saturday and she emerged from the collapsed building three hours later.
A Red Crescent spokeswoman was quoted as saying the woman "doesn't have a single scratch on her face". No other survivors have been found since three were rescued on Thursday.
"God kept me alive," said the woman, Shahr-Banu Mazandarani, after her dramatic rescue on Saturday. She survived because wooden roof beams fell across her, forming a protective cavity which stopped bricks from crushing her, a senior Red Crescent official said.
Doctors say she has no broken bones, although she is in a state of shock and is being treated at a Red Crescent Medical Centre in Bam.
Experts say it is very unusual for anyone to survive even beyond three days without food or water in earthquake rubble. In previous cases, reports of miraculous rescues several days after an earthquake have often proven to be false.
The tremor destroyed or damaged 90% of buildings in the historic mud-brick city. More than 30,000 people died in the Bam quake and some 100,000 have been left homeless. Officials say the full death toll may never be known.
Rescue
The Red Crescent spokeswoman, quoted by Reuters, said Mrs Mazandarani "can talk to us and answer our questions - when I ask her something she says 'yes, dear'".
Rescuers said they had first heard a weak voice from the rubble and soldiers had spotted a hand protruding from the rubble. They then started digging the woman out.
"Chai" - the word for tea - was among her first words. When handed a cup of tea, she pushed it away and said: "It's hot. Don't give it to me now".
Experts say the death toll in Bam was so high because many buildings built in violation of construction codes collapsed quickly, leaving no chance for the occupants to escape or survive in air pockets.
Iranian state media said at least three of Bam's 23 schools were reopened briefly on Saturday.
Aid workers remain concerned about poor sanitary conditions in the devastated city - but refuse services were back in action on Saturday.
Thousands of Iranian volunteers have flooded into Bam to help survivors.
Running water and electricity have been restored to some areas, and trucks are delivering water to other points.
, it give me chills.
