The paper aims at clarifying the meanings of conscience and guilt in Heidegger's Being and Time. It is divided into four sections. After a brief introduction to the leading question of the paper (section one), we discuss the meaning of Heidegger's existential death (section two). Heidegger's explication is framed under the perspective of Dasein's whole-being (Ganzsein), which is understood by him as Dasein's between birth and death. Then (section three) I discuss his existential conscience and guilt. Conscience calls us away from our inauthentic self and towards authentic self. Guilt reveals our existential nothingness. Heidegger's explication of the nature of conscious and guilt is according to my observation still under the perspective of his existential solipsism. Finally in the last section (section four) I conclude Heidegger's insight and discuss some possible problems, especially about the problems of absolut other and dialects of Dasein, that imply in Heidegger's existential solipsismus.