1. A service system which is configured with one or more computers and performs a failure prediction of a plurality of monitored systems, wherein the one or more computers are configured to: receive measured values regarding a plurality of indexes from the monitored systems; designate a prediction model for predicting a future measured value from the received measured values, from a plurality of prediction models, regarding a reference index which is a part of the plurality of indexes; predict a predicted value of the reference index based on the designated prediction model; generate a plurality of Bayesian networks targeting the reference index and a target index which is an index that is a part of the plurality of indexes but different from the reference index; store the generated Bayesian networks in a memory or a storage of the one or more computers; and calculate a probability that a measured value of the target index will become a predetermined value or fall within a predetermined value range based on the predicted value of the reference index, and a Bayesian network that is designated from the plurality of Bayesian networks by a received input, wherein the predetermined value or predetermined value range that is used defines a predicted failure with respect to the plurality of monitored systems.