The former Girls Aloud singer joined the talent show in 2008 and two of her acts went on to win the show – Alexandra Burke and Joe McElderry.
Cheryl left the judging line-up in 2010 before returning again in 2014.
The Newcastle born star mentored last year’s runners-up, Reggie N Bollie, who finished behind 17-year-old Louisa Johnson.
The 32-year-old said in a statement: “I have had such an amazing experience being a judge on the X Factor.
“I have learnt so much and enjoyed nurturing talent but I’ve missed making music and am excited to be recording again.
“I want to thank everybody I have worked with along the way, especially Simon, who I love to bits. I hope the show continues to produce stars and I wish them all the best.”
The show’s boss, Simon Cowell, said: “Cheryl and myself spoke about this. I totally understand her commitment to making more records. She has been amazing on the show, and in the near future we will be working on other things together.”
Cheryl has started working on a new album which is due for release later this year.
Her exit follows the news that DJ Nick Grimshaw will not be returning as a judge.
The show’s presenters, Caroline Flack and Olly Murs, also confirmed they would not return.
An X Factor spokesman said: “Cheryl has been a great judge and mentor during her time on the X Factor, from her early years of winning with two of her acts – Alexandra Burke and Joe McElderry – through to last year’s series where she took Reggie N Bollie into the final.
“We’d like to thank Cheryl for her contribution to the show and wish her all the best with her return to music.”