Disclosed are a modular controller and an operating method thereof. An operating method of a modular controller having a plurality of modules in a software-defined network environment includes generating a first event including a message that is received from a network device, transmitting the first event to an event handler, transmitting the first event to the plurality of modules from the event handler, determining whether the first event is identical to a target event in event type through the plurality of modules that receive the first event, and performing a function of a first module, which corresponds to the identity between the first event and the target event, by using the first event. A network manager is able to easily form a controller with various functions such as performance enhancement and security enhancement at need, facilitating combination and separation of different modules in a controller.