We formulate a holographic description of effects of disorder in conformal<br />
field theories based on the replica method and the AdS/CFT correspondence.<br />
Starting with $n$ copies of conformal field theories, randomness with a<br />
gaussian distribution is described by a deformation of double trace operators.<br />
After computing physical quantities, we take the $n \to 0$ limit at the final<br />
step. We compute correlation functions in the disordered systems by using the<br />
holographic replica method as well as the formulation in the conformal field<br />
theory. We find examples where disorder changes drastically the scaling of two<br />
point functions. The renormalization group flow of the effective central charge<br />
in our disordered systems is also discussed.