1. A fault detection device, comprising: a measurement data acquirer configured to acquire measurement data for current flowing through power supply lines connected to multiple electrical devices; a clusterer configured to classify the measurement data for a past fixed period into multiple clusters based on at least one of frequency and phase with respect to an AC cycle; a pattern determiner configured to determine, for each cluster of the multiple clusters, an appearance pattern of the measurement data satisfying a preset standard; and a fault determiner configured to determine that a fault has occurred to an inhabitant when measurement data additionally acquired does not match the appearance pattern determined by the pattern determiner.