Skew product Compact group extension Central Limit TheoremWe investigate the dynamical properties of a skew product transformation T ϕ on [0, 1) × G defined by T ϕ (x, g) = (T x, g · ϕ(x)) where T is the β-transformation for β 2 and ϕ(x) is a compact group G-valued step function with a finite number of discontinuities. We give several sufficient conditions for ergodicity and strong mixing of T ϕ . As an application, we describe a class of step functions which satisfy the Central Limit Theorem for the β-transformations. As another application, we also consider a class of skew product transformations T β,a,w on [0, 1) × [0, 1) which maps (x, y) → (βx, y + ax + w) (mod 1) where a, w ∈ R and give necessary and sufficient conditions for ergodicity and strong mixing.