Agree with the above - if you're talking about an adult Corn and adult mice, then it should be getting one mouse a week max. On average, mine get one adult mouse every two weeks.
In the wild they're opportunistic feeders, so don't be fooled if yours exhibits constant hunting behaviour and appears to be hungry; that's just what they're programmed to do. They're designed to cope with long periods of time without food in the wild, and the strategy for dealing with lack of prey persists in captivity, even when their next meal is guaranteed.
In captivity they're capable of scoffing anything you give them until they throw up, and then come looking for more! You have to act as a sort of Weightwatchers Group Leader on their behalf, otherwise they'll end up obese and dead before their time.