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, wherein the clusterer separates or classifies the measurement data for the past fixed period based on at least one of frequency and phase with respect to the AC cycle, and classifies the separated or classified data into the multiple clusters based on a correlation of the data, and wherein the clusterer classifies the measurement data for the past fixed period based on the phase with respect to the AC cycle, and classifies the classified data into the multiple clusters based on the correlation of the data.