With respect to a housing device having a plurality of slots in which plug-in units are mountable, division plates corresponding to the positions of the openings of the slots are put in the inside of a baffle section for changing the direction of the flow of cooling air released from the slots, and the division plates are used to divide the inside space of the baffle section into a plurality of regions corresponding to the slots, thereby reducing mutual interference of the cooling air from the slots in the baffle section and preventing a further increase in differences in the amount of passing air among the slots. Thereby, even if any difference occurs in the amount of passing air among the slots due to a structural factor, it is possible to reduce the deterioration of the cooling capacity of a slot through which relatively less amount of air passes.