This video explains the earliest existing evidence of hominids using fire— potentially being as early as 1.5 million years ago.  It is likely that Homo Erectus were the first to use fire, as evidenced by their teeth becoming more like modern humans which suggests that they often cooked their food, and their brain size rapidly grew due to increased calories from meat consumption.  Strangely though, there is evidence of humans widely migrating throughout the world before evidence of the use of fire has been found.