We fabricated thin-film magnetoimpedance elements in which an impedance of each 100 μm section of element can be examined, to investigate impedance changes of each section subjected to a DC magnetic field. The field strength where the impedance peaks shows a larger value at the edge and it decreases toward the center of the element, while the sensitivity is small at the end of the elements and increases toward the center of the element. The obtained results can be explained on a basis of magnetic field simulation and simple impedance model taking into account a distribution of demagnetizing field. A uniformity of demagnetizing field is significant to obtain a higher sensitivity, and intensity of the demagnetizing field strongly affects a magnetic field strength when the impedance peaks. We also clarified an ellipsoidal shape uniform the distribution of demagnetizing field within the element, which contributes to improve the sensitivity of the MI sensor, especially near edge part.