TOKYO, Oct 25 (Reuters) - Japanese stocks rose on Tuesday as earnings season started, with investors hopeful that electric motor maker Nidec Corp's strong results could be a positive sign for other companies that might stand to benefit from a weakened yen.

The Nikkei share average opened up 0.51% and extended gains to 0.84% by the midday break.

The broader Topix index gained 0.81%.

Nidec was the Nikkei's best performer, jumping 4.76%, after reporting record second-quarter operating profits, helped in part by the yen's decline.

The Japanese currency has fallen more than 20% against the U.S. dollar this year, with 6% of that coming in the July-September quarter.

"Nidec's earnings were welcomed by the market," Nomura Securities equities strategist Kazuo Kamitani told reporters.

"With the effect of the weak yen at record highs and the solid growth in electronic vehicle sales, we can't say this will have a big influence on the entire market, but it should help firm expectations for upcoming earnings reports."

Shares in Nidec are down more than 38% this year, compared to the Nikkei's 5.53% fall. The company has been embroiled in management turmoil this year, with its former chief executive officer leaving the company last month after receiving a demotion in April.

"The results this time were not to my satisfaction yet, but the business performance is already on the way to recovery," said company founder and returning CEO Shigenobu Nagamori after the earnings release.

Chugai Pharmaceutical Co Ltd was the Nikkei's biggest decliner, falling 3.18% despite reporting a 35.7% year-on-year increase in operating profit for the nine months ended Sept. 30.

Each of the Nikkei's 11 sectors advanced, with energy and technology leading gains. Of the index's 225 constituents, 203 rose while 19 fell and three traded flat.

The Topix index's 33 industrial sectors also all gained. (Reporting by Sam Byford; Editing by Rashmi Aich)