UPDATE 1-Norway's wealth fund doubled its return on investment in 2017

* Norway fund is world's largest sovereign wealth fund

* Graphic: http://tmsnrt.rs/2tskfub (Adds detail, graphic, bullets)

OSLO, Feb 27 (Reuters) - Norway's $1 trillion sovereign wealth fund, the world's largest, doubled its return on investment in 2017, beating its own benchmark, as strong global stock markets boosted the value of the portfolio, it said on Tuesday.

The fund earned a return of 13.7 percent in 2017, up from 6.9 percent in 2016.

"The fund's cumulative return since inception has passed 4,000 billion Norwegian crowns ($511.18 billion). One out of four crowns of return was generated in 2017, after a very strong year for the fund," CEO Yngve Slyngstad said in a statement.

"Again, our equity investments returned strongest with a return close to 20 percent."

The fund's biggest single investment was in Apple Inc , worth 66 billion crowns, ahead of Nestle on 51 billion and Royal Dutch Shell on 50 billion.

Apple was also the biggest single contributor to the fund's returns in 2017, ahead of Chinese tech group Tencent Holdings and Microsoft. ($1 = 7.8250 Norwegian crowns)

(Reporting by Gwladys Fouche and Alisted Doyle, editing by Terje Solsvik)