An image forming apparatus includes a fixing unit having a heater and fixing a toner image formed on a recording material onto this recording material. The heater includes a first heat-generating member and a second heat-generating member, a first driving element provided on a power supply path to the first heat-generating member; a second driving element provided on a power supply path to the second heat-generating member, a control unit controlling the first driving element and the second driving element respectively, first detection unit for detecting current flowing through the first heat-generating member, a second detection unit of detecting current flowing through the second heat-generating member, and a safety circuit receiving a first output of the first detection unit and a second output of the second detection unit.