Another hint that Japan's strong export driven recovery may be losing steam, and with it, the surging growth in Australia's export earnings.

For the third month in a row the country's annual export growth eased, according to figures from the country's Ministry of Finance.

While that might be partly due to exports in May of last year not being as low as earlier in that year, it does also reflect the slowing pace of demand, especially from Asia and China.

Exports fell 1.2% in May from April after April's exports were up more than 2% from February.

But exports in May were still up 32.1% from May, 2009, that's less than the 37% rise forecast by the market.

Despite signs of slowing, exports were still up for the sixth month in a row.

Japan's export growth is likely to continue to slow over coming months, because business restocking is ending and the Chinese economy is going off the boil.

Both developments contain not so good news for Australian exports, especially iron ore and coal.

And for companies like BHP Billiton and Rio Tinto.

Imports were up 33.4%, thanks mostly to higher prices for commodities like oil, iron ore, coking and thermal coal. The market had been looking for a rise of just over 34%.

Exports to Asia, which account for more than half of the country's total shipments, were up 34.4% from May 2009, down on the 45% annual rate in April.

Exports to China were up 25.3% from a year earlier, But that was down from the 41% rate in the year to April.

Shipments to America rose 17.7% in the year to May.

Australia did well; imports from here jumped 40.6% thanks to higher prices for iron ore and coal.

Japan's exports to Australia from Japan were up 32%.

The Japanese finance ministry said the data showed no effects from Europe's debt problems.

Shipments to the European Union rose an annual 17.4%, tanks in part to strong demand for auto parts and electronics parts from Germany where exports are strong.

Exports accounted for around 0.7 of Japan's 1.2% March quarter economic growth, which was stronger than the US or Europe.

Japan's trade balance was 324.2 billion yen ($US3.61 billion) in May, up 15.2%.