A method and a device for transmitting updated information for an ML reconfiguration in a wireless LAN system are proposed. Specifically, a reception MLD performs an ML reconfiguration with a transmission MLD. The reception MLD transmits MLD capability information for the ML reconfiguration to the transmission MLD. The transmission MLD comprises a first transmission STA operating in a first link and a second transmission STA operating in a second link. The reception MLD comprises a first reception STA operating in the first link and a second reception STA operating in the second link. The MLD capability information includes information on a change in the number of links supported by the transmission and reception MLDs at the same time.