: This study intended to explore fundamental causes affecting consumers' response actions from psychological factors in the situation of sellout occurring during shopping in online fashion stores. In addition, this study devised a virtual online shop in order to measure consumers' cognitive and emotional psychological responses they experienced when goods were sold out. The subjects involved women in 20s~30s, major customers of online shopping, and the subjects were randomly allocated to one of eight questionnaire forms (2(stockout size: high vs low)×2(product assortment similarity: similar vs. dissimilar)×2(restocking cue: included vs excluded)). The number of final data used for the analysis was 336 and through SPSS 21.0 program, two-way ANOVA and bootstrap were utilized. The analysis result was that consumers' psychological responses (emotions, psychological reactance) of online shops differed by means of varying stockout situations. The stockout size had positive effect on psychological reactance and negative emotions. On the other hand, there was no difference in positive emotions (arousal) according to stockout size. In stockout situation of online fashion store, the moderating effect of product assortment similarity and restocking cues were verified. According to the analysis result, interaction effects between stockout size and restocking cues, product stockout size and product assortment for psychological reactance were significant. Lastly, the mediation effect of psychological reactance and emotion between stockout size and behavioral response was tested. As a result, the moderated mediation effects of psychological reactance for substitute were significant when product assortment was dissimilar and restocking cue was exclude.