An image processing apparatus, which includes a voice input receiver configured to receive a voice input of user, a signal processor configured to recognize and process the received voice input received through the voice input receiver, a buffer configured to store the voice input, and a controller configured to determine whether a voice recognition function of the signal processor is activated and control the signal processor to recognize the voice input stored in the buffer in response to the voice recognition function being determined to be activated. The controller is further configured to store the received voice input in the buffer in response to the received voice input being input through the voice input receiver while the voice recognition function is not activated, so that the received voice input is recognized by the signal processor when the voice recognition function is activated.