An excrement detection system of this disclosure includes: an excretion information acquiring apparatus acquiring excretion information indicating whether a pet in a living space has performed excretion； a toilet observing apparatus observing inside of a pet toilet to acquire toilet information regarding inside of the pet toilet； an excretion information processing unit determining whether the pet has performed excretion based on the excretion information； a toilet information processing unit determining whether the pet is in the pet toilet based on the toilet information； an excretion position determining unit determining that the pet has performed excretion outside of the pet toilet when determined that the pet has performed excretion and that the pet is absent from the pet toilet； and a notifying unit notifying a pet's owner that the pet has performed excretion outside of the pet toilet when determined that the pet has performed excretion outside of the pet toilet.
