Attentional bias toward threatening stimuli is recognized as 1 of the most important cognitive vulnerability factors for anxiety. However, the association between anxious attention and negative moods has not been fully elucidated, particularly in terms of the effect of such bias on mood fluctuations in daily life. We examined the associations between attentional bias and emotional dynamics under a daily life setting. Participants (46 university students) completed the dot-probe task in the laboratory, after which they entered a 6-day experience sampling measurement to assess temporal fluctuations of momentary levels of anxious mood and occurrence of stressful events. The results showed that attentional bias was significantly correlated with increased temporal instability of anxious mood. Furthermore, attentional bias was also associated with enhanced emotional reactivity immediately after occurrence of the stressful event, but not with either the sensitivity to detect stressors or to the recovery process aimed at calming the stress-induced anxious mood on a longer time scale. These findings suggest that attentional bias is associated with the acute impact of a stressor on moods, as evidenced by the increased temporal instability and stress-reactivity of anxious mood.