Particularly, it is an object to provide a circuit substrate that can reduce a field intensity near an electrode having a high potential. A circuit substrate of the present invention includes an insulated substrate, a thin-film resistive element, and electrodes electrically connected to both sides of the thin-film resistive element, the thin-film resistive element and the electrodes being disposed on a surface of the insulated substrate. The circuit substrate is characterized in that the thin-film resistive element has a pattern in which a resistance wire is repeatedly folded back, and a dummy wire for reducing a field intensity is provided on a high-potential electrode side.