Sir Michael - who took over the role after Richard Harris died - said it was sometimes a bit of a nuisance but it's important to keep smiling and be nice to his young fans.
He said: "My friends' children come round and see me now, which they never did before.
"Being Dumbledore is a big responsibility."
But playing Dumbledore obviously hasn't proven that big a job, because since filming began in February he's had time to make three other films!