Provided is a fixing device whose required heat generation amount can be obtained with a smaller amount of a microwave absorbing material, hence start-up (warm-up) time for achieving fixable temperature of the fixing device can be shortened without impairing characteristics such as flexibility, releasing property, durability. The fixing device comprises: a heating member; a pressurizing member; and a microwave generating unit, the fixing device being configured to fix an unfixed toner on a recording material by passing the recording material through a nip formed between the heating member and the pressurizing member, wherein: the heating member includes a heat generating layer for generating heat with microwave generated by the microwave generating unit; and the heat generating layer contains a high molecular compound and a carbon fiber having an average fiber diameter of 80-150 nm, an average fiber length of 6-10 μm, and in Raman spectrum, an absorption peak resulting from graphite structure.