Muscle tissue isn't made out of thin air. If you gain muscle mass, you have also gained bodyweight - how do you think that happens? You don't think that a guy with a 40 inch chest and his twin that built a 50 inch chest really weigh the same, do you?
Do you think Arnold Schwarzenegger weighed 150lbs?
Even if one were to not lift weights at all, do you think you can get fatter without eating an excess of calories? Of course not, and that's just fat tissue which we all know weighs less than muscle tissue.
Of course you need to eat an excess of calories if you want to build an excess of muscle. Besides needing to get the energy and building material from somewhere, your body also needs to be in an environment where it feels comfortable building new muscle tissue (a physiologically expensive process that it will not do if it thinks you might be starving sometime in the near future).
If you want to gain muscle, you should be eating 1.5 grams of protein per pound of bodyweight daily (the building blocks of muscle), a moderate amount of fat (for joints, hormones, and energy), and enough carbs to gain several pounds of bodyweight each month (usually somewhere around 2xbodyweight in grams of carbs, depending on how much fat you're getting in your diet)
Don't try to figure out some exact formula here, you are going to need to tweak it through trial and error anyway... just get a decent bodybuilding diet going, and if you haven't gained at least 1lb after two weeks of it, you need to eat more.
You also have to do this every single day, without fail (as well as training at least 5 days a week), for several months on end to see the results you're after. For every day that you fail to reach your dietary quotas during the week, go ahead and cut the results you expect to see in half. Consistency is really that important in bodybuilding.