A method and an apparatus for transmitting a wakeup packet in a wireless LAN system are proposed. Specifically, a transmitter generates a wakeup packet by applying an OOK scheme. The transmitter transmits the wakeup packet to a receiver via an 80 MHz channel. The 80 MHz channel includes first to fourth subchannels. If some of the first to fourth subchannels are busy or there are no pending wakeup packets for the receiver in some of the subchannels, some of the subchannels are punctured. The wakeup packet is transmitted via the remaining subchannels of the first to fourth subchannels. Each of the first to fourth subchannels is a 20 MHz channel.