A sensor apparatus according to an embodiment of the present invention includes an element substrate, an element electrode located on an upper surface of the element substrate, an insulating member covering at least a part of the element electrode, and a detection part that includes an immobilizing film located on the upper surface of the element substrate or an upper surface of the insulating member, and performs a detection of a detection object contained in a specimen. A surface roughness of the immobilizing film is smaller than a surface roughness of the element electrode. In a sensor apparatus of other embodiment of the present invention, an amount of oxygen in a surface layer part of the immobilizing film is smaller than an amount of oxygen in a surface layer part of the element electrode.