This paper analyzes how two types of negative interrogative expressions in Japanese, p-naika and p-janaika, are distinguished depending on the circumstances under which they are used. This paper proposes the following: p-naika is able to be used only when the speaker cannot judge, or perceive that he or she cannot judge p to be true or false. p-janaika is able to be used only when the speaker can judge p to be true or false, and judge p to be true. In addition, this paper presents the analysis that the difference mentioned above between p-naika and p-janaika comes from the difference of their own respective structures that indicate the factual level and the judgement level.