Disclosed is a speech processing method. The speech processing method controls activation timing of a microphone based on a response pattern of the microphone from a user in order to implement a natural conversation. The speech processing device and the NLP system of the present disclosure may be associated with an artificial intelligence module, a drone (or unmanned aerial vehicle (UAV)), a robot, an augmented reality (AR) device, a virtual reality (VR) device, a device related to 5G service, etc.