The official Petra news agency reported on Monday that the blast happened when a prospective buyer was looking at merchandise in the shop in Khalidiyah in northern Jordan.
A bomb detonated, killing the buyer and the shop owner instantly, the agency said.
A police official said the authorities believed that the explosion was caused by unexploded ordnance among the scrap metal of Iraqi military origin.
There was no indication of a bomb having been planted in the shop, which sells iron rods and other scrap imported from Iraq, the officer said, speaking on condition of anonymity because he was not authorised to make press statements.
The village is on the outskirts of Mafraq, 70km (43 miles) north of the Jordanian capital, Amman.
The police officer identified the dead men as Moussa al-Azazmeh and Anas Ali.
Jordan prohibited the importation of Iraqi scrap metal early last year after reports that Jordanian scrapyards contained parts of Iraqi missiles that could have been contaminated with radioactive material.