A determination device includes an image information acquirer configured to acquire image information of a subject image obtained by photographing an internal space of a toilet bowl in excretion; an estimator configured to perform estimation regarding a determination matter relating to excretion by inputting the image information to a learned model, the learned model having learned a correspondence relationship between an image for learning and a determination result of the determination matter relating to excretion, the learned model learned by machine learning using a neural network, the image for learning representing an internal space of a toilet bowl in excretion; and a determiner configured to perform determination regarding the determination matter of the subject image based on an estimation result obtained by the estimator.