The No Doubt frontwoman wed the British rocker in London on September 14, 2002 and they are parents to two sons, Kingston, six, and Zuma, four.
The couple is now getting ready to celebrate its milestone wedding anniversary on Friday and Stefani has revealed her marriage to Rossdale is her proudest achievement, reported Marie Claire magazine.
"(It is) a miracle. My biggest accomplishment is my marriage so far. Because it's hard, everyone knows it's hard. (Marriage) is something that I always wanted to do successfully.
It was a dream of mine. I like the official-ness and the family-ness of it all, having the same name and making decisions together... "(Our relationship) is better than it's ever been.
Like, we're learning about each other all the time. He's an amazing dad, he works so hard... He balances me out. And he - he never stops liking me, which is awesome. It makes me feel happy, that someone likes me as much as he does," said Stefani.