A fixing apparatus to fix a toner image formed on a recording material to the recording material includes a rotatable member having a heat generation layer, a power supply circuit, and a control unit. The power supply circuit supplies electrical power to the rotatable member. The control unit controls supply of electrical power to the rotatable member and detects a change rate of electrical resistance of the heat generation layer. The heat generation layer generates heat by the electrical power supplied to the rotatable member, and the toner image on the recording material is fixed to the recording material by the heat from the heat generation layer. If the change rate of the electrical resistance to the supplied electrical power is higher than a predetermined threshold, the control unit stops the supply of electrical power to the rotatable member.