Mitchell joined the Spireites in the summer of 2016 after leaving Chelsea.
The 22-year-old scored two goals in 32 appearances during his time at the Proact.
His final appearance came last night when he was handed a starting role in the Derbyshire Senior Cup match against Belper Town.
Manager Jack Lester said: “Reece leaves the club with our good wishes and we wish him all the very best for the future.”