Provided is an apparatus for diagnosis and prediction of a severe accident in a nuclear power plant. The apparatus comprises a classification unit configured to derive a plurality of scenarios for diagnosis and prediction of the severe accident in the nuclear power plant; a strorage medium storing instructions for executing a method for diagnosis and prediction of the severe accident in the nuclear power plant using a learning model trained by a training database including training input variables for the plurality of scenarios and severe accident diagnosis and prediction information corresponding to the training input variables; and a processor configured to obtain diagnostic input variables for the diagnosis and prediction of the severe accident in the nuclear power plant, input the diagnostic input variables into the learning model to check the severe accident diagnosis and prediction information, and output the checked severe accident diagnosis and prediction information.