This study shows, through a series of computer simulation on the role that altruistic behavior plays in particular social relations, that acting in an altruistic way can bring out outcomes that is beneficial to the actor him/herself. The present study specifically focuses on the individual-to-individual kind of altruistic behavior, not on the individual-to-collectivity type. It was shown that “downward OFT” strategy with a moderate level of others' worth, when this strategy is shared by all group members, promotes altruistic behavior in the group. Specifically, results of computer simulations show the followings: In the situation where group members select the target of their altruistic action on the basis of whether the target him/herself acted altruistically in the past, ones who act altruistically toward more people do receive more benefit from others than those who did not act so altruistically.