Boil water and cook the macaroni according to the directions on the box.
While the macaroni is cooking, melt the butter in a sauce pan. Stir in the flour. Add the milk slowly. Cut the cheese into small pieces and add it to the milk mixture.Stir until the cheese is melted being careful not to let it burn on the bottom of the sauce pan.
Drain the macaroni when it is cooked.
Mix the cooked macaroni with the cheese mixture in a pan.
Cover the pan and bake it covered at 350 deg. for 45 minutes.