The 33-year-old England international, who earlier this month signed a new contract extending his stay at Old Trafford until 2027, was charged after being sent off in the 78th minute of United's 2-2 draw at Bournemouth last month.
The FA said that Maguire was alleged to have "acted in an improper manner and/or used abusive and/or insulting words and/or behaviour towards the fourth official following his dismissal".
He admitted the charge and has also been fined 30,000 pounds.
United will also be without Argentine centre back Lisandro Martinez, who will miss the club's next three matches - against Chelsea, Brentford and Liverpool - after receiving a red card for violent conduct in Monday's 2-1 home defeat by Leeds United.
Martinez was sent off in the 56th minute for pulling the hair of Leeds striker Dominic Calvert-Lewin.
United, who are third in the standings with 55 points from 32 games, travel to sixth-placed Chelsea on Saturday.