An information output device that outputs monitoring information including monitoring logs generated by monitoring devices, and includes: memory; and a processor coupled to the memory. The processor, by using the memory, operates as: a receiver that sequentially receives monitoring logs, each including a monitoring result indicating whether a monitoring target has an anomaly; a manager that manages, based on the monitoring logs, a first state that is a state of anomaly occurrence in a monitoring target of each of the monitoring devices; a storage that stores path information indicating transmission paths, each indicated by one or more devices through which a monitoring log transmitted by a source passes; a determiner that determines the reliability level of each received monitoring log based on a first transmission path of the monitoring log and the first state; and an outputter that outputs, based on the reliability level, monitoring information including the monitoring log.