A drum type heat exchanger for effectively ventilating and purifying room air of a factory, a building or a house and the like is described. The drum type heat exchanger has heat transfer means with a drum shape and thus an entire size is reduced as much as possible and become compact, such that a handling and an installation is easy, a thermal efficiency to an installation space of the heat transfer means is maximized, and overall maintenance and repair such as a check or exchange of the heat transfer means are easy. Additionally, the drum type heat exchanger uses a drum with a short radius of rotation so that an entire operation cycle time is shortened and a heat transfer area is sufficiently secured in order to keep the thermal efficiency high.