Yes and No. It depends what you mean by "big."
Normally a well fed kitten will have what I refer to as "a fat belly," reflecting their stomach being full of food. One of their main jobs at this stage in life is to store food and grow as fast as possible. The more they can gorge themselves the longer they can survive when mom is away hunting.
A skinny kitten is reason for concern, and should be taken to the vet. To judge skinny and fat you really have to have seen a fair amount kittens.
Kai's advice is perfect IMO: It is good to take your new animals to the vet and you can work out when to immunize them and get them fixed etc. If the kitten is active, playful, eating and eliminating and you have no reason to believe something is wrong with it, it is probably healthy.
If you think the kitten's belly is too big or the kitten has other symptoms take it too the vet.