Provided are a method and an apparatus for receiving a downlink signal in a wireless communication system. The method includes receiving resource block assignment information including a bitmap and receiving the downlink signal through a resource block group (RBG) indicated by the bitmap in a bandwidth part. A total number of resource block groups (RBGs) in the bandwidth part is determined based on an index of a start resource block of the bandwidth part, a size of the bandwidth part, and a size of one resource block group.