An image capturing method and an image-capturing device thereof are provided. Firstly, a dividing rule for dividing a first part and a second part is set, such that the positions and sizes of the first and the second parts are obtained accordingly. Next, a first resolution corresponding to the first part and a second resolution corresponding to the second part are set respectively. Then, the positions and sizes of the first and the second parts, the first resolution and the second resolution are recorded in a reference table. Next, an image of an object is captured to obtain a multi-resolution analog signal. Then, the multi-resolution analog signal is transformed to a multi-resolution digital signal. After that, a first part image corresponding to the first part and a second part image corresponding to the second part are respectively obtained with reference to the multi-resolution digital signal.