The benchmark Nikkei index at the Tokyo Stock Exchange fell 54.29 points to 9,422.88. The Topix index was off 0.17 percent, or 1.42 points, at 817.74.
Technology shares were dragged down by weakness in US tech stocks overnight, Kazuhiro Takahashi, general manager of investment strategy and research at Daiwa Securities, told Dow Jones Newswires.
Toshiba lost 4.16 percent to 414 yen and TDK was down 2.51 percent at 4,065 yen.
Toshiba on Tuesday said its plans to win $12 billion in orders to build nuclear reactors may have to be delayed for several years as nations tighten safety after Japan's March 11 seismic disaster and atomic crisis.
Sony dropped 1.49 percent to 2,236 yen, following news on Tuesday that its websites in three countries had been hacked with 8,500 Greek user accounts compromised.
Sony also said Wednesday hackers have attacked Sony Ericsson's Canadian eShop website, affecting 2,000 users, the latest online strike against the Japanese electronics and entertainment giant.
Investor sentiment was also dampened by concerns over China's twin threats of a slowing economy and still-high inflation, brokers said.
Japanese heavy machinery companies that export to China were pressured by the weakness in the Shanghai market. Komatsu was off 1.57 percent to 2,379.
Carmakers were higher in the wake of media reports that Toyota is planning to bring its domestic production schedule forward, despite the fact the automaker denied having set firm new targets.
Toyota rose 2.15 percent to 3,315 yen as Honda gained 1.32 percent to 3,065 yen.
There was little impact from data released shortly before the opening bell that showed Japan plunged into a trade deficit in April as exports tumbled 12.5 percent year-on-year due to supply chain disruptions after the March 11 earthquake and tsunami.
Japan logged a deficit of 463.7 billion yen ($5.6 billion) in the month, reversing a year-before surplus of 729.2 billion yen. The deficit, however, was smaller than the market average forecast of 700 billion yen.
Investors had very low expectations and "any downside is already digested after last week's dismal GDP numbers", Takuya Yamada, senior portfolio manager at ITC Investment Partners, told Dow Jones.
Government data last week showed Japan's economy plunged back into recession in January-March, ravaged by the impact of the earthquake, tsunami and a subsequent nuclear crisis considered the worst since Chernobyl in 1986.
Copyright AFP (Agence France-Presse), 2011