Modern industrial systems combine discrete and continuous behaviors and thus are hybrid systems (HSs). In this brief, we introduce a new definition of diagnosability of HSs called $h$ -diagnosability, and we present a method to verify this property. The method is based on a verifier automaton that can be constructed in polynomial time, leading to a smaller computational complexity for the verification of the diagnosability of HS than methods using diagnoser automata. The main idea is to build a verifier of the underlying discrete-event system, taking into account the distinguishability of the system modes based on the continuous state models of the HS.