Rumination has been associated with impaired attentional control. People with ruminative tendencies may experience problems in everyday life because they fail to divide attention between internal and external information; they must cope with external events even as they become trapped in rumination. To clarify the characteristics of negative rumination, we investigated the relationship of negative rumination (“negative rumination trait” and “uncontrollability of negative rumination”) with divided attention between internal and external information. Fifty-eight university students performed a divided attention task (dual task) consisting of (1) a primary, external attention task, in which they were asked to press a button corresponding to the location of an asterisk displayed on a computer screen, and (2) a secondary, internal attention task, in which they were asked to retrieve words from memory. The results showed that the capacity of divided attention was correlated with “negative rumination trait” in men and with “uncontrollability of negative rumination” in women, suggesting that people with higher ruminative tendencies had more difficulty dividing attention between internal and external information.