After his visit to the diplomat, Stocker told The Associated Press that he saw wounds on Sharafi's body that "were several weeks old", but said he did not know how the injuries occurred.
"I cannot say who did it and where it happened," the ICRC official said. "I can only say that it happened during his detention."
Stocker was accompanied to the hospital by Majid Sheikh, the Iraqi ambassador to Iran.
Diplomat accuses US
Earlier in the week, Sharafi's Iranian doctors had reported that holes had been drilled into his foot, but the TV images were not clear enough to indicate whether the small, red marks on his foot were indeed holes.
Doctors also reported earlier that he had suffered a broken nose, serious injuries to his back, bleeding in his digestive system, and damage to his ears.
None of these injuries has been independently verified, nor were they discernible from the TV footage.
Footage released by Iranian TV showed Jalal Sharafi in hospital being examined by doctors
A spokeswoman for the ICRC in Tehran, Katayoun Hosseinnejad, confirmed the visit to Sharafi had taken place and said it had been initiated by the Iranians.
Sharafi was released from Iraq last week and later said that the CIA had questioned him about Iran's relations with Iraq and its assistance to various Iraqi groups.
US officials have repeatedly said that Iran provides money and weapons to Shia militias in Iraq. Iran has denied this.
On Wednesday the US military put more weapons on display in Baghdad  that it said were made in Iran.
An army spokesmen said that Iran had trained Iraqi insurgents in the use of roadside bombs as recently as last month.