Abstract: Based on the conception of cognitive gap inducting from balance theory,congruity theory,and the theory of cognitive dissonance,the study exams how the Internet rumors spread on the virtual world through the great social event of Hung Chung-Chiu Case in 2013 Taiwan,by investigating the relationships between cognitive gap,trust attitude,rumor believing,and retransmitting behavior. By way of applying an empirical questionnaire survey with 604 respondents,the results showed that the larger peoples' cognitive gap is,the more they distrust in the military as well as the government,the easier they believe rumors,and in turn the more they will spread misinformation online. Besides,cognitive gap has not only a direct effect,but also an indirect effect via rumor believing and,in turn,retransmitting behavior. This finding reveals that rumor believing plays an important and significant mediating role with respect to peoples' cognitive gap. However,such a crucial mediator role is not discovered on the trust attitude toward military and government.