The present invention relates to a wireless communication system. The present invention relates more particularly to a method and an apparatus for receiving a downlink signal by a device in a wireless communication system, the method comprising the steps of: receiving from a subframe a first PDCCH comprising scheduling information about first common data; receiving from the subframe a second PDCCH comprising scheduling information about second common data; and, on the basis of Ta, a TB size of the first common data and Tb, a TB size of the second common data, controlling a procedure for receiving downlink data from the subframe, wherein if T1