Abstract: The present invention provides a device for predicting prognosis of a patient who undergoes PEG, which allows a doctor to obtain predictive results sufficient to judge whether or not to perform the PEG (percutaneous endoscopic gastrostomy) for the patient. This device includes: a prognosis prediction expression storage section 14 configured to store a prognosis prediction expression, the prognosis prediction expression being calculated by applying prediction input factors and prediction output factors about a first patient who already underwent the PEG, to ANN (artificial neural network); and a processing section 16 configured to: receive diagnosis input factors about a second patient, for judging whether or not to perform the PEG on the second patient; calculate diagnosis output factors in response to the diagnosis input factors based on the prognosis prediction expression; and output the calculated diagnosis output factors.