(Updates with closing prices)

By Kevin Buckland

TOKYO, Nov 7 (Reuters) - Japan's Nikkei share average

sank on Friday, sending the index to its biggest weekly drop

since early April, as heavyweight tech stocks tracked an

overnight decline in U.S. peers amid worries about stretched

valuations.

The tech-heavy Nikkei ended the day down 1.2% at

50,276.37, taking its loss for the week to 4.1%.

That's after rising to an all-time peak of 52,636.87 on

Tuesday, the start of a holiday-shortened week in Japan.

In October, the benchmark index rallied 16.6% to book

its best month in 35 years.

Overnight, investors returned to selling the darlings of the

artificial intelligence-fuelled rally that carried Wall Street,

Tokyo and other global bourses to successive record peaks in

recent months. Nvidia ( NVDA ) slid 3.7% and AMD dropped 7.3%.

In Japan, startup investor SoftBank Group

dropped 6.7% and chip-testing equipment maker Advantest ( ADTTF )

, a Nvidia ( NVDA ) supplier, slumped 5.5%, making them

the Nikkei's top two decliners in index-point terms.

"Rather than a change in the way investors fundamentally

view AI stocks, there is this risk-off mood around how fast

these stocks have rallied," said Nomura Securities strategist

Fumika Shimizu.

Corporate results are also key for the market now, with

Japan's earnings season currently in full swing, she said.

The three biggest percentage decliners on the Nikkei on

Friday all posted disappointing financial results. Environmental

equipment supplier Kanadevia ( HIZOF ) tumbled more than 19% and

confectionary maker Ajinomoto ( AJINF ) and electronic component

manufacturer Taiyo Yuden ( TYOYF ) each shed more than 16%.

The biggest percentage gainer was also driven by corporate

results, with HR technology firm Recruit Holdings ( RCRRF )

jumping more than 16%.

Embattled automaker Nissan Motor ( NSANF ) got some respite

after reporting a return to operating profit. Its shares climbed

4.3%.

Among the Nikkei's 225 components, 102 rose versus 123 that

fell.