I never felt inclined to doubt his existence until you pressed me on it. Now I feel the need to research the diverging viewpoints. It would seem that there are 3 main camps here...
1. Moses existed and wrote the 1st 5 books of the Bible
2. Moses existed and may have authored some of the 1st 5 books.
3. Moses never existed, and his name is a Hebrewised version of Ahmose, a Pharoe of the period.
I think he probably existed.