Gnanduillet, who was part of Spireites’ 2013/14 League Two winning team, currently plays for Hearts and is expected to complete the deal inside the next 48 hours.
Despite interest from several English Football League clubs and National League side Wrexham, the 29-year-old is content to return to his homeland.
Wrexham want Gnanduillet to help their promotion push towards League Two, while Sheffield Wednesday have also been tracking him but they have other options.
The Edinburgh Evening News revealed last month that Salford City were also keen on Gnanduillet after watching him fall down the pecking order in Scotland. Their manager, Gary Bowyer, coached the player at Blackpool but they have yet to make a formal offer for his services.
Le Mans play in the Championnat National, the French third tier, and Gnanduillet is happy to move there in order to revitalise his career after falling completely out of favour at Tynecastle.