The disclosure provides an additional learning device, an additional learning method, and an additional learning program . The additional learning device includes: an acquisition unit (12) acquires information based on data observed in a control object which is controlled by an instruction in accordance with an output from a previously learned model outputting an objective variable with respect to an explanatory variable. A determination unit (14) determines whether or not the explanatory variable corresponding to the information acquired by the acquisition unit (12) exists as learning data of the model, that is, whether or not the explanatory variable is unknown. When the explanatory variable is determined to be unknown by the determination unit (14), an additional learning unit (16) acquires the objective variable corresponding to the unknown explanatory variable, correlates the unknown explanatory variable and the acquired objective variable, and additionally learns the model. The model is updated with regard to unknown disturbance events without requiring manpower.