The announcement comes weeks after Kier’s new top boss Andrew Davies launched a review to cut debt and simplify the group’s structure.
The firm said it had started the search for his replacement when he leaves at the end of September.
Dew, aged 48, joined Kier over four years ago, quitting his job then as finance director of Balfour Beatty’s regional construction business where he had been in post just over a year.
Before that he was the chief financial officer of Lend Lease’s UK and European construction business for four years.
Philip Cox, Kier chairman, said: “Bev has been our finance director for over four years and I would like to thank him for his contribution over this time.
“Bev remains firmly committed to the company and will be working with the board to deliver the 2019 results.”
Davies started the top-to-bottom review of the £4bn revenue business to look at further ways of simplifying Kier to create a more focused group.
He said the review would build on work that has been undertaken by the board in recent months and was additional to the previously announced Future Proofing Kier programme, initiated by former chief executive Haydn Mursell.