* Key index at +8, matching peak hit in April
* Firm Nikkei, hopes for strong earnings boost sentiment
* Investors focus on trends in Asian markets, Fed policy
By Chikafumi Hodo and Mari Terawaki
TOKYO, Jan 21 (Reuters) - Japanese retail investors turned optimistic towards domestic stocks in January, with a key index matching a nine-month peak as stronger share prices in Tokyo boosted confidence, a Reuters survey showed.
A bright outlook for Japanese corporate earnings also helped bolster sentiment.
"Japanese corporate earnings are expected to improve further in the second half of the year, so the outlook for Japanese share prices will be even stronger," said an investor in his 50s.
The Reuters sentiment index, calculated by subtracting the percentage of investors who say they are bearish from those that are bullish, posted its first positive reading since April.
The index rose 10 points to plus 8 in January, matching a three-year high reached in April, following the biggest-ever improvement, of 58 points to minus 2, the previous month.
Investor sentiment has been improving in tandem with Japan's benchmark Nikkei average, which has climbed 3 percent this year and 15 percent since the start of November.
The Reuters survey of 407 Japanese individual investors was conducted Jan. 12-15, during which the Nikkei hit an eight-month intraday high of 10,620.57 on Jan. 13 after foreign investors continued to pile in to Japanese equities.
Retail investors remain concerned the yen could strengthen again, but major falls in the Japanese currency would prompt more inflows into domestic shares, investors said.
The yen stood at around 82-83 against the dollar during the survey, near its level during the previous poll, held slightly over a month ago.
"A strong recovery in the U.S. economy could weaken the yen to around 90 (to the dollar). That would be positive for the Japanese economy and share prices," an investor in his 60s said.
The poll showed that about 60 percent of investors believed market trends in China and other Asian countries would be the key theme for Japanese equity markets this year.
Investors also said the trend for easing monetary policy in the United States and the outcome of the debt crisis in the euro zone would be important factors for the market in 2011.
The poll showed that 55 percent of respondents thought the extension of tax breaks for investment in securities or a corporate tax cut would be positive for stocks, while 43 percent said such steps would have no impact.
The monthly poll, which is conducted anonymously, aims to capture the views of readers of an online magazine targeted at users of the Reuters Japan website http://www.reuters.co.jp (Reporting by Chikafumi Hodo; Editing by Joseph Radford)