The present invention provides various thin-film sensor type power measuring apparatuses which can be constructed in a simplified and compact structure so as to measure the power of high-frequency circuits or batteries. This power measuring apparatus includes: a magnetic film disposed in parallel to a primary conductor through which a load current flows; a power supply with input and output terminals for supplying an element current to the magnetic film; a bias magnetic field applying unit for applying a DC magnetic field in a direction that is parallel, perpendicular, or diagonal to the direction of magnetization of the magnetic film; and a detection unit for detecting the voltage between the ends of the magnetic film in the direction of the element current. The power measuring apparatus detects only the DC voltage component between the ends of the magnetic film in the direction of the element current.