The core data, which exclude volatile demand from power companies and for ships, beat the market expectation of a 4.7-percent rise and rebounded from an 8.2-percent drop in July and a 7.7-percent increase in June.
Strong demand from manufacturers of electronic and information technology machinery boosted the orders, according to the data released by the Cabinet Office.
The report was "positive because the data showed business investment is picking up, especially in manufacturing sectors," said Takeshi Minami, chief economist at Norinchukin Research Institute.
A similar trend was also shown in the latest "tankan" business sentiment survey, released last week by the Bank of Japan.
However global uncertainty was expected to discourage further corporate spending, analysts said.
"Business spending will lose its growth momentum" because "exports are expected to slow down due to weakening in the global economy," Minami said.
Slow political progress in Japan to approve a fresh extra budget could prompt companies to delay their spending related to reconstruction projects for the northeastern region hit hard by the March disasters, he added.