The present research investigated the effect of causal attribution on social-comparison jealousy. A pilot study showed that causes attributed in jealousy-provoking situation were categorized in terms of the following three dimensions: internality, stability, and direction of cause. In study 1, 256 female students assessed the feelings of jealousy on six emotion adjectives in two hypothetical jealousy-provoking situations, in which the dimensions of cause were manupulated. The result showed that only the dimension of internality among the three dimensions was related to jealousy, i. e., social-comparison jealousy was aroused in greater degree the by external attribution than by internal attribution in two situations. In study 2, 57 female students participated and assessed their locus of control and strength of jealousy in the two situations. The result showed externals exhibited more jealousy than internals in one situation. These results suggest that external attribution causes social-comparison jealousy, but that the effect varies depending upon importance of situation.