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: (1) receive measured values regarding a plurality of indexes from the monitored systems; (2) 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; (3) predict a predicted value of the reference index based on the designated prediction model; (4) generate or update a Bayesian network 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; and (5) 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 the Bayesian network.