A heater plate includes a sheet-like heating member that generates heat upon being energized, a protective film provided on the side of one major surface of the sheet-like heating member to protect the sheet-like heating member, an output circuit section provided on a surface of the protective film on the opposite side to the sheet-like heating member, and a protruding portion forming film provided between the protective film and the sheet-like heating member. The output circuit section has protruding portions formed to be capable of respectively abutting terminals of a heat flux sensor which is an inspection object. The protruding portion forming film has protrusions at positions corresponding to the protruding portions. The sheet-like heating member, the protective film, the output circuit section and the protruding portion forming film are integrally formed into one piece.