A state detector of a video device and a state detection method thereof are provided. The state detector includes a first chroma detector, a second chroma detector, and a controller. The first chroma detector and the second chroma detector operate in a first state among a plurality of states. When the second chroma detector is not capable of processing an input signal normally, the controller controls the second chroma detector to switch between the states until the second chroma detector operates in a second state to process the input signal normally, and the first chroma detector is set to operating in the second state. As a result, the quality of a displayed image is improved.