Let R be a finite Blaschke product of degree at least two with R(0) = 0. Then there exists a relation between the associated composition operator C R on the Hardy space and the C * -algebra O R (J R ) associated with the complex dynamical system (R •n ) n on the Julia set J R . We study the C * -algebra T C R generated by both the composition operator C R and the Toeplitz operator T z to show that the quotient algebra by the ideal of the compact operators is isomorphic to the C * -algebra O R (J R ), which is simple and purely infinite.