In the context of observers, any mathematical model according to the viewpoint of an observer $ \Theta $ is called a relative model. The purpose of the present paper is to study the relative model of logical entropy. Given an observer $ \Theta $, we define the relative logical entropy and relative conditional logical entropy of a sub-$ \sigma_\Theta $-algebra having finitely many atoms on the relative probability $ \Theta- $measure space and prove the ergodic properties of these measures. Finally, it is shown that the relative logical entropy is invariant under
the relation of equivalence modulo zero