A communication technique that combines a 5G communication system for supporting a data rate that is higher than that of a beyond 4G system with IoT technology, and a system thereof are provided. The technique may be applied to intelligent services on the basis of 5G communication technology and IoT related technology, such as smart home, smart building, smart city, smart car or connected car, health care, digital education, retail, etc. A method of performing access deregistration by a user equipment (UE) and an apparatus therefor are provided. The method includes, when the UE is registered on both 3rd generation partnership project (3GPP) access and non-3GPP access, transmitting, to an access and mobility management function (AMF), a deregistration request message to deregister the non-3GPP access over the 3GPP access, and receiving, from the AMF, a deregistration accept message corresponding to the deregistration request message over the 3GPP access.