The Ministry of Economy, Trade and Industry said the penalty on Seishin Enterprise Co. for violating the Foreign Exchange and Foreign Trade Law will be effective on December 5.
The two-year export ban is the longest penalty available under the law, a ministry official said.
According to the ministry, the Tokyo-based firm shipped a jet-mill grinder in 1999 and another in 2000 to Iran without government authorization.
In 2004, two executives of the company received suspended jail terms and a court ordered the firm to pay a fine of 15 million yen (129,000 dollars) for the illegal shipments worth 15 million yen.
A jet mill uses compressed air to grind solid materials — such as medicine and printer toner ink — into fine powder, but it also can be used to increase the burning efficiency of solid rocket fuel.
Japan’s trade controls law lists the jet mill along with other items, such as rocket launchers, as strategic goods that require approval from the trade minister for export.
The penalty comes amid mounting concern about Iran, which has rebuffed demands to halt uranium enrichment that could be used to develop nuclear weapons.