Passive immune therapy with“trastizumab” have been proven to be useful to treat HER-2/neu overexpressing breast cancers. However,serious problems such as recurrence presumably due to the resistance acquisition occasionally occur. Therefore, several peptide vaccines have been studied to overcome the problems. Several peptides have been shown to elicit specific immune response and expected to confer a clinical benefit. The interactions between the peptides and specific HLA molecules are crucial for the proper immune response. Hence, understanding the detailed molecular mechanisms of the interactions are of particular interest from the view point of designing better peptide vaccines. In this study, the interaction modes between these peptides and HLA-A*24:02 which is the most common allele in Japanese populations were elucidated by docking simulations. The roles of each amino acid of these peptides in immunization deduced from the present study would be useful for designing more potent and specific peptide vaccines.