The Grammy Award winner singer - who made her acting debut in 'Soul Surfer' - has beaten off competition from former contestants Kelly Clarkson, Oscar winner Jennifer Hudson and Adam Lambert to take the top spot with earnings of $20 million.
Adam Kluger, the president of brand partnership company the Kluger Agency told Forbes magazine: "['American Idol' is] a money-making machine. It's like having the Super Bowl every week."
The first 'American Idol' winner Kelly has made $2.5 million from the show.
However host Ryan Seacrest has beaten all of the previous competitors making $61 million from his presenting role and associated endorsements and deals.
Forbes list of highest-paid 'American Idol' contestants
1. Carrie Underwood: $20 million
2. Chris Daughtry: $6 million, Adam Lambert: $6 million
3. Fantasia Barrino: $4 million
4. Jordin Sparks: $3 million
5. Kelly Clarkson: $2.5 million
6. Jennifer Hudson: $2 million
7. Kellie Pickler: $1.8 million
8. Clay Aiken: $1.5 million