A machine learning-based method for prediction of breast cancer prognosis using next-generation sequencing comprises the steps of: allowing a computer device to use RNA sequencing data of a subject tissue to measure an expression level of a target gene; allowing the computer device to input the expression level of the target gene into an artificial neural network adapted beforehand; and allowing the computer device to estimate the prognosis of breast cancer of the subject on the basis of the output value of the artificial neural network. The artificial neural network is adapted beforehand to have target gene expression levels of multiple samples as input values and to output results depending on oncotype DX recurrence scores for the multiple samples.