An image forming apparatus, comprising: a fixing portion configured to fix an image formed on a recording material onto the recording material, the fixing portion includes a heater (300; 600; 900; 903; 1000) which includes a substrate, a plurality of heat generating blocks (HB1 to HB7) arranged on the substrate in a longitudinal direction of the substrate, and a plurality of temperature detecting elements (Tl-1 to Tl-7, T2-2 to T2-6) disposed on the substrate; and a control circuit (400; 700; 901; 904; 1001) configured to control power to be supplied to the plurality of heat generating blocks (HB1 to HB7), the control circuit (400; 700; 901; 904; 1001) includes an electromagnetic relay, a plurality of semiconductor elements (441 to 447) connected between the electromagnetic relay and the plurality of heat generating blocks (HB1 to HB7) and configured to perform switching between ON and OFF of the plurality of heat generating blocks (HB1 to HB7), and selectively controls the power to be supplied to the plurality of heat generating blocks (HB1 to HB7) by selectively controlling the plurality of semiconductor elements (441 to 447), wherein out of the plurality of heat generating blocks (HB1 to HB7), a first semiconductor element (441, 447) to supply power to a first heat generating block (HB1, HB7) is provided in a first current path between a branch point of a second current path and the first heat generating block (HB1, HB7), and is connected, in series, to a second semiconductor element (442, 446) to supply power to a second heat generating block (HB2, HB6) out of the plurality of heat generating blocks (HB1 to HB7), the second heat generating block (HB2, HB6) is controlled by controlling the second semiconductor element (442, 446), the second current path is a current path between the second semiconductor element (442, 446) and the second heat generating block (HB2, HB6), and the first heat generating block (HB1, HB7) is controlled by controlling the first semiconductor element (441, 447) and the second semiconductor element (442, 446). a fixing portion configured to fix an image formed on a recording material onto the recording material, the fixing portion includes a heater (300; 600; 900; 903; 1000) which includes a substrate, a plurality of heat generating blocks (HB1 to HB7) arranged on the substrate in a longitudinal direction of the substrate, and a plurality of temperature detecting elements (Tl-1 to Tl-7, T2-2 to T2-6) disposed on the substrate; and a control circuit (400; 700; 901; 904; 1001) configured to control power to be supplied to the plurality of heat generating blocks (HB1 to HB7), the control circuit (400; 700; 901; 904; 1001) includes an electromagnetic relay, a plurality of semiconductor elements (441 to 447) connected between the electromagnetic relay and the plurality of heat generating blocks (HB1 to HB7) and configured to perform switching between ON and OFF of the plurality of heat generating blocks (HB1 to HB7), and selectively controls the power to be supplied to the plurality of heat generating blocks (HB1 to HB7) by selectively controlling the plurality of semiconductor elements (441 to 447), wherein out of the plurality of heat generating blocks (HB1 to HB7), a first semiconductor element (441, 447) to supply power to a first heat generating block (HB1, HB7) is provided in a first current path between a branch point of a second current path and the first heat generating block (HB1, HB7), and is connected, in series, to a second semiconductor element (442, 446) to supply power to a second heat generating block (HB2, HB6) out of the plurality of heat generating blocks (HB1 to HB7), the second heat generating block (HB2, HB6) is controlled by controlling the second semiconductor element (442, 446), the second current path is a current path between the second semiconductor element (442, 446) and the second heat generating block (HB2, HB6), and the first heat generating block (HB1, HB7) is controlled by controlling the first semiconductor element (441, 447) and the second semiconductor element (442, 446).