The main purpose of this paper is investigation of the Bayes Formula problem for Klement's fuzzy probability measure. This measure is defined here on a family of fuzzy subsets which is, among other things, closed under complement given as an involution satisfying Zadeh's Extension Principle. Due to Ovchinnikov's result [6], we express this complement as a variable pointwise involution. Next we prove that the Bayes Formula holds for fuzzy probability measure iff it is a fuzzy P-measure, more generally defined here. Moreover, we show that there exists an automorphism between fuzzy probability space with the usual Zadeh operator of complement and fuzzy probability space with Ovchinnikov's operator of complement. So, using the Bayes method of inference, we can always replace the generalized operator of complement by Zadeh's one.