The present invention relates to a new cyclic peptide compound or a salt thereof, which has anti-hepatitis C virus activities based on inhibitory activity against the RNA replication of hepatitis C virus replicon, to a process for preparation thereof comprising a rearrangement reaction under a mild acidic condition and the following amino acid changing reactions etc., to a pharmaceutical composition comprising the same, and to a method for prophylactic and/or therapeutic treatment of hepatitis C in a human being or an animal.
