A method of classifying data includes: training a classification model for classifying input data into at least one class, such that a first output value is generated according to a second equation in which a component corresponding to a label distribution of source data is disentangled in a first equation corresponding to the classification model; generating a second output value by applying, to the first output value, information indicating a label distribution of target data; and classifying the target data into the at least one class by using the second output value.