This study investigated the effect of the use of humor in negative political messages on attitudes towards candidates and voting preference. Specifically, this study tested the effect of humor not only on attitudes toward the speaker candidate but also toward the target candidate. Relative favorability toward the speaker candidate to the target candidate was also measured. An online experiment was conducted utilizing a local major election situation(N=450). Participations were exposed to a political speech delivered by a candidate who harshly criticized a rival candidate either with humor or without humor. The results showed that negative political messages has a negative effect on attitudes toward the speaker candidate. Negative political messages with humor was found to be less effective in degernerating attitudes toward the target candidate than those without humor. Relative favorability toward the message-sender candidate was found to be higher for the no humor message than for the humor message. Theoretical and practical implications were discussed.