To improve the high-frequency response of inductance in thin-film inductors with square spiral shape (SS-shape), it is important that the directions of the magnetic hard axis and the exciting field should be the parallel to each other. Methods of controlling the magnetic anisotropy of CoNbZr films with SS-shape by means of heat treatment were investigated. In positive magnetostrictive films, whose magnetic easy axis in as-made state is oriented to the diagonal of the square, rotating-field annealing treatment changes the direction of the easy axis to that of the square spiral. This knowledge was used to fabricate inductors with SS-shapes whose inductance when the magnetic anisotropy of their core is controlled shows a large value and a flat frequency response.