This paper aims to use a critical discourse analysis (CDA) to analyze types of online news headlines about COVID-19 on cruise ship, the Diamond Princess, and to identify different traits between conservative newspapers and progressive ones. 480 articles were collected from five major news outlets in Korea: Chosun Ilbo, Joongang Ilbo, Donga Ilbo, Hankyoreh, and Kyunghyang Shinmun. The results show that the headlines tend to contain negative or extreme vocabulary and to employ quotes from experts or even from unknown sources in order to criticize Japan and blame the Japanese government for their way of dealing with the situation. In the case of differences between politically biased sources, it was found that the conservative media inclines toward framing negative images of the Japanese government by publishing more articles than the progressive media and by using numbers and statistics to clearly describe the surge of infected people on the ship. They also published more articles than the progressive media about Korea's actions to bring Koreans back home from the ship, framing positive images about the Korean government. As can be seen, the online news headlines are politically biased and manipulatively framed, so readers' discretion is necessary.