1. A plant model management device comprising: a generation unit configured to receive a first set of prior probability distributions of a first set of automatic operation parameters, the first set of automatic operation parameters defining a condition required for modeling a plant model, and the plant model being a model based on data concerning a plant, and generate a first set of posterior probability distributions of the first set of automatic operation parameters and a first set of probabilistic plant models based on the first set of prior probability distributions, the first set of posterior probability distributions reflecting compatibility with learning data, and the learning data being past time-series data concerning a first explanatory variable and a first objective variable; and a combining unit configured to combine the first set of probabilistic plant models using the first set of posterior probability distributions to generate a first plant model.