A communication technique of integrating a 5th generation (5G) or pre-5G communication system for supporting a higher data transmission rate after a 4th generation (4G) communication system such as long term evolution (LTE) with an IoT technology, and a system thereof. The disclosure may be applied to an intelligent service (for example, a smart home, a smart building, a smart city, a smart car, or a connected car, health care, digital education, retails, security and a safety related service, and the like) based on the 5G communication technology and the IoT related technology. According to various embodiments, a device and a method for optimizing mobile initiated communication only (MICO) mode related parameter values for reducing power consumption of a terminal in a mobile communication system.