TOKYO, Oct 5 (Reuters) - Japan's Nikkei share average rebounded from an over four-month low on Thursday as investors scooped up beaten-down stocks, with easing U.S. Treasury yields supporting sentiment.

The Nikkei was up 1.18% to 30,886.51 by the midday break, after falling to its lowest level since May 18 in the previous session. For the week, however, the index has lost 3% so far.

The broader Topix rose 1.44% to 2,250.93.

"Investors were prompted to buy back stocks after sharp declines in Japanese equities this week and U.S. Treasury yields eased," said Jun Morita, general manager of the research department at Chibagin Asset Management.

"But they will be cautious about making active buying before confirming U.S. economic data such as payrolls report, which could set directions of U.S. yields."

Longer-dated U.S. Treasury yields eased from 16-year highs overnight, after data showed that U.S. jobs growth was below economists' expectations in September.

Investors are now cautiously awaiting the U.S. non-farm payrolls data due on Friday.

Chip-testing equipment maker Advantest jumped 4.31% to give the biggest boost to the Nikkei, while Tokyo Electron rose 1.55%.

Monex Group surged 17.89% to its daily limit high after Japanese mobile operator NTT Docomo said it formed a capital tie-up with the fintech firm to build a new financial services business.

Japan Exchange Group, the operator of the Tokyo Stock Exchange, surged 5.38% to become the top performer on the Nikkei, followed by Aozora Bank, which rose 4.64%.

Daiwa Securities Group rose 4.43%, helping the brokerage sector climb 4.09%, making it the top performer among the 33 industry sub-indexes. (Reporting by Junko Fujita; Editing by Varun H K)