Abstract: The present disclosure relates to a gateway device supporting integral processing of APIs with security function, and a method of operating the gateway device. In more detail, the present disclosure relates to a gateway device for integrally processing APIs with a security function, the gateway device supporting a security function that notifies of a security danger when a problem is generated by analyzing logs in the process of API calling and responding and supporting a security function that increases security for a new environment in which calling of several API servers and responding are repeated in a gateway by applying a function of integrally processing a plurality of API functions by registering the API functions into a unit API service to the gateway, and a method of operating the gateway device.