Disclosed are a method and a device for performing transmission/reception on the basis of a time unit group in a wireless communication system. According to one embodiment of the present disclosure, a method by which a terminal receives a downlink channel in a wireless communication system comprises the steps of: receiving configuration information about a slot group; monitoring a downlink control channel in one or more search space (SS) sets on the basis of the slot group; and receiving downlink control information (DCI) in the downlink control channel, wherein one or more from among the period, the offset and the duration of the SS sets can be set on the basis of granularity M (M is an integer greater than 1) of the slot group.