A film heater includes a transparent conductive film and first and second electrodes. The transparent conductive film includes a heat generating portion that generates heat when energized by the first and second electrodes. An outer edge of the heat generating portion has a short side, a long side, and first and second oblique sides. The first and second electrodes include a plurality of first and second connection portions corresponding to a plurality of first and second ports, respectively. A plurality of first and second current suppression portions is disposed to suppress flow of the current between the inside and outside of the heat generating portion through a region between the plurality of first and second ports, respectively. For each of some or all of the plurality of first ports, the current flows through the heat generating portion between the first port and at least two second ports.