  For $0\le \alpha <1$ and $\beta>2$, we consider a linear mod 1 transformation
on a unit interval; $x\mapsto\beta x+\alpha$ (${\rm mod}\ 1$), and prove that
it satisfies the level-2 large deviation principle with the unique measure of
maximal entropy. For the proof, we use the density of periodic measures and
Hofbauer's Markov Diagram.
