An apparatus for evaluating the effect of a drug comprising; an image obtaining unit configured to obtain a plurality of evaluation target images captured in different fields of view depicting a subject to which the drug is administered under a same administration condition, wherein an administration condition is a dose of the drug or exposure time of the drug, wherein the exposure time is an elapsed time from when the drug is administered until when imaging of the subject is performed; a probability obtaining unit configured to obtain a plurality of recognition probabilities by obtaining a recognition probability regarding each of the evaluation target images by using a model that outputs, in accordance with input of an image, the recognition probability at which a subject of the image is recognized as the subject before effect of the drug is expressed or the subject after the effect of the drug is expressed; a calculation unit configured to calculate an expression degree of the effect of the drug, which refers to a degree to which the subject is changed due to the effect of the drug, and wherein the expression degree is calculated as a representative value or a variance of the plurality of recognition probabilities regarding the plurality of evaluation target images; a training data obtaining unit configured to obtain training data including only a pre-expression image depicting the subject before the effect of the drug is expressed and a post-expression image depicting the subject after the effect of the drug is expressed; and a training processing unit configured to execute training process of the model by using the training data, wherein the pre-expression image is an image depicting the subject before the drug is administrated, and the post-expression image is an image depicting the subject after the effect of the drug is expressed to a maximum extent. an image obtaining unit configured to obtain a plurality of evaluation target images captured in different fields of view depicting a subject to which the drug is administered under a same administration condition, wherein an administration condition is a dose of the drug or exposure time of the drug, wherein the exposure time is an elapsed time from when the drug is administered until when imaging of the subject is performed; a probability obtaining unit configured to obtain a plurality of recognition probabilities by obtaining a recognition probability regarding each of the evaluation target images by using a model that outputs, in accordance with input of an image, the recognition probability at which a subject of the image is recognized as the subject before effect of the drug is expressed or the subject after the effect of the drug is expressed; a calculation unit configured to calculate an expression degree of the effect of the drug, which refers to a degree to which the subject is changed due to the effect of the drug, and wherein the expression degree is calculated as a representative value or a variance of the plurality of recognition probabilities regarding the plurality of evaluation target images; a training data obtaining unit configured to obtain training data including only a pre-expression image depicting the subject before the effect of the drug is expressed and a post-expression image depicting the subject after the effect of the drug is expressed; and a training processing unit configured to execute training process of the model by using the training data, wherein the pre-expression image is an image depicting the subject before the drug is administrated, and the post-expression image is an image depicting the subject after the effect of the drug is expressed to a maximum extent.