Dublin in Joyce`s works is not just a geographical location but a synecdoche for the colonial chronotope Ireland. In his representation of this temporal-spatial entity, Joyce`s perspective is different from that of the Irish mainstream cultural and political movements. While the latter is engaged in eulogizing and elegizing at the same time, absorbing both themselves and the masses in sentimentality over their own colonial fate on the one the hand and hatred against the empire on the other, Joyce is laughing all the time with different tonalities to perform the functions of ridicule, criticizing, subverting and finally utopian imagining. So his laugh is more like the laughter of Democritus invoked by Bakhtin in his study of Rabelais and his world, namely, it has a philosophical character. For Joyce, he uses this art of laughter to achieve a sober and an in-depth understanding of his nation`s own maladies and ugliness so as to demolish them as a preparation for reconstructing a new space. To achieve this purpose, Joyce has created two characters, Stephen and Bloom, with the former to perform the function of demolishing and the latter to perform the function of reconstructing. In my paper, with regard to their images, their physical and mental activities throughout the novels A Portrait and Ulysses against their specific historical, economic and cultural background, I use the Benjaminian concept “Flaneurie” and the Jamesonian concept “cognitive mapping” to interpret the mode and the implication of their images and activities, highlighting the transcendent and critical perspective thus endowed to them by Joyce in contrast to the immanent and entrapped perspective of their fellow citizens. The conclusion is that, with the double actions of these two characters, Joyce, just as Richard Ellmann says, has actually created not one but two Ulysseses in his national epic. Their flaneurie and mapping constitute the Irish version of Odyssey, a journey to open the way for national revival based on spiritual liberation.