The brisk exports pumped up the nation's trade surplus 15-fold to Y742.3 billion from Y48.9 billion in the same month a year earlier, the Ministry of Finance data showed.
The data indicate Japan's economy is off to a strong start in the April-June quarter, after expanding at a solid 4.9% annualized rate in the previous three months.
Japan's economic prospects are still under threat from Europe's debt turmoil and consequent rises in the yen. But the continuing signs of economic improvement may give some relief to Prime Minister Yukio Hatoyama's government, which is working to shore up diminishing popularity before a planned Upper House election in July.
Exports have grown more than 40% on year every month since January, providing crucial support to an economy in which domestic demand is still heavily dependent on stop-gap government support.
Auto exports to the rest of the world jumped 103.1% on year in April, retaining their momentum from the 110.8% surge in March, the highest since 1980 when comparable data were first made available. Auto exports increased 105.0% in February.
U.S.-bound car shipments rose 105.3% on year in April, the data showed, an indication that Toyota's massive recalls in recent months have done little to damp overall demand for Japanese cars.
Overall imports climbed 24.2% in April to Y5.147 trillion, the ministry said.