This study attempts at constructing a wholistic concept of justice that integrates both social justice and eco-justice into one: socio-eco justice. There has been some diversion of concern in the advocators of social justice and those of eco justice. The former is concerned about the problem of justice within human society, while the latter, especially deep ecologists, is about the problem of justice in the natural environment. The author employs the “ontology of the void or nothing” of Alain Badiou, a contemporary French philosopher, in order to substantiate the author`s idea of socio-eco justice. First, he formulates the idea of ecological environment as a concept bridging between the human society and the nature. Ecological environment points to the nature involved in the human society. The nature in the form of ecological environment participates in the human society and its political situation. Second, the author, employing the ideas of presentation and representation by Alain Badiou, argues that the subaltern (the nothing in the human society) and the ecological environment are presented, but not represented, in today`s capitalistparliamentary society. The un-representation of these elements in the situation causes incessant instability in the society. Justice in a wholistic conception is the inclusion of the two un-represented elements, the subalterns and the ecological environment, who have been treated as the objects of exploitation and as nothing and the void, into our political situation as participatory subjects. Socio-eco justice based on the “subtractive ontology” (or, ontology of the void) of Alain Badiou can give us some direction toward a new civilization of justice.