How many officials are on the field during a foot ball game?

Answer 1

In pro and College Football, there are seven: A referee, back judge, side judge, line judge, field judge, umpire, and head linesman. Check out this link to read about their specific duties on the field:

http://en.wikipedia.org/wiki/Official_(American_football)

Answer 2

4. One is the main official refree. And two are the lines man and the last one is the time official