This study analyzes the loss peak frequency of an integrated ferromagnetic noise suppressor by evaluating the demagnetizing field. An integrated ferromagnetic noise suppressor is fabricated using a regular silicon process, and relation between the loss peak frequency and demagnetizing field is evaluated. The demagnetizing factor is calculated by approximating the magnetic film by a slender ellipsoid. Measurements of a fabricated on-chip noise suppressor reveal that the loss is maximized at 7 GHz, which is equal to the calculated ferromagnetic resonance (FMR) frequency. Then, the relation between the loss peak frequency and FMR frequency are discussed with some magnetic films in our previous works. The loss peak frequencies in coplanar lines of various magnetic films with different ratios of the film thickness to the signal line width agree well with the FMR frequency of magnetic films. This result reveals that the shift of the loss peak depends on the demagnetizing field over a wide frequency range. Consequently, the loss peak frequency of the integrated ferromagnetic noise suppressor can be controlled as a function of demagnetizing field in the magnetic film.