Provided is a carbon dioxide supply assistance device that: measures the environment inside and outside a greenhouse in which plants are raised; obtains environmental conditions; calculates the rate of exchange of carbon dioxide by the plants in the greenhouse on the basis of, from among the environmental conditions, carbon dioxide concentrations inside and outside the greenhouse, the greenhouse ventilation frequency, and the light intensity in the greenhouse; generates environmental data in which the environmental conditions and the rate of exchange of carbon dioxide are associated with each other; obtains, from among the environmental data that an environmental data generating unit previously generated, similar environmental data which are similar to the environmental conditions; calculates the rate at which the plants in the greenhouse consume the carbon dioxide in the greenhouse on the basis of the similar environmental data and the rate of exchange of carbon dioxide; and estimates the relationship betwee
