Provided is a method of processing a user input to deliver the user input to at least one of a plurality of assistants, includes: converting a user input including a voice signal based on a predetermined rule to generate an instruction; splitting a complex instruction into partial instructions based on that the generated instruction is the complex instruction requesting two or more events; and determining a domain of each of the partial instructions and distributing the partial instructions to at least one of a plurality of voice assistants based on the domain. According to an embodiment, the washer may be related to artificial intelligence (AI) modules, unmanned aerial vehicles (UAVs), robots, augmented reality (AR) devices, virtual reality (VR) devices, and 5G service-related devices.