Nope! It's Miror B with only two r's. If you really want to be technical it's also 'Miror B.' with the dot. Case in point, his Japanese name is Mirorbo, and most importantly how it is spelt in the game.
http://bulbapedia.bulbagarden.net/wiki/Miror_B.
http://bulbapedia.bulbagarden.net/wiki/Miror_B.