Fuente: WIPO "tomato" A growth state estimation apparatus comprises a concentration acquisition unit which acquires a carbon dioxide concentration at a first time point in a plant factory and a carbon dioxide concentration at a second time point after the first time point, detected by a sensor provided in the plant factory, a supply amount acquisition unit which acquires a supply amount of carbon dioxide supplied from the first time point to the second time point in the plant factory via carbon dioxide supply equipment having a tank for storing carbon dioxide, a consumption amount identification unit which identifies a consumption amount of carbon dioxide consumed by a plant being cultivated in the plant factory from the first time point to the second time point, and an estimation unit which estimates a growth state of the plant.