The country's current account surplus in July rose 58.1 percent from a year earlier to 1.14 trillion yen, according to a preliminary report released Thursday by the Finance Ministry.
The figure marked the 10th straight month of increase.
The current account is the broadest gauge of trade, measuring the difference between a country's income from foreign sources and foreign obligations payable, excluding net capital investment.
The current account combines trade, services, income and current transfers.
Led by increased exports to Asia, the surplus in goods-and-services trade soared 326.6 percent from a year earlier to 423.1 billion yen. The 326.6 percent growth was the largest year-on-year increase since July 1997, according to the ministry. It added, however, that the jump was at least partially due to the relatively low figure marked in July 2001.
The surplus in merchandise trade -- exports minus imports -- grew 60.5 percent on a year-on-year basis to 916.5 billion yen, marking the fifth consecutive month of increase.
Exports grew 8.9 percent from a year earlier to 4.17 trillion yen, an increase for four consecutive months, mainly due to an increase in exports of electronics components to the rest of Asia and automobile exports to Asia, Europe and the United States.
Imports eased 0.2 percent to 3.25 trillion yen, marking the 12th straight month of decline.
In July, the yen averaged 118.07 against the dollar, a 5.3 percent appreciation compared with 124.68 a year ago. In contrast, the yen averaged 117.17 against the euro, a 9.4 percent depreciation from 107.09 a year before.
Crude oil prices stood at 19,538 yen per kiloliter during the same month, a 9.8 percent decrease from a year earlier.
The deficit in the services account grew by 21.5 billion yen to 493.4 billion yen mainly because the deficit in royalties and license fees increased.
The income balance surplus increased by 130.7 billion yen to 825.5 billion yen, marking the first year-on-year increase in two months.