An exhaust emission control device including a casing, and a downstream exhaust passage, which extends substantially perpendicular to an axis of the casing and receives an exhaust gas flow from an outlet of the casing, is disclosed. The casing accommodates a particulate filter as a post-treatment device through which exhaust gas is passed for cleanup. In order to realize compactness in size of the whole structure without increasing exhaust resistance, an outer chamber encases the casing in a required range to provide required spacing for an open end and an outer periphery of the outlet of the casing. The outlet chamber intervenes between the outlet of the casing and the downstream exhaust passage.