A digital device and controlling method thereof are disclosed. The digital device according to an embodiment of the present invention includes a display unit configured to output a content and a controller. The controller is configured to obtain content information of the content being outputted, obtain at least one associated keyword corresponding to the obtained content information, retrieve at least one piece of associated information related to the content using an associated search term containing the obtained at least one associated keyword, and to output the retrieved at least one piece of the associated information.