TOKYO, Aug 11 (Reuters) - Japan's Nikkei share average edged down on Tuesday after China devalued the yuan by nearly two percent, with investors taking profits as they assessed the ramifications of Beijing's move to support the economy and exports.

The Nikkei average fell by 0.4 percent to close at 20,720.75 after first nearing the 18-1/2-year high it marked earlier this year.

The broader Topix fell 0.2 percent to 1,687.60, erasing Monday's gains that saw it reach an 8-year high. The JPX-Nikkei Index 400 fell 0.2 percent to 15,219.52.

Shares in steel and other companies with strong ties to China proved resistant to profit taking, rising on hopes of further stimulus after China's central bank devalued the yuan.

(Reporting by Joshua Hunt; Editing by Eric Meijer)