An image forming apparatus includes: an annular endless belt; a drive roller, around which the endless belt is wound and which moves the endless belt; a first tension roller, around which the endless belt moved by the drive roller is wound; a biasing mechanism connected to the first tension roller and including an elastic member that applies a tension to the endless belt via the first tension roller; a second tension roller, around which the endless belt moved by the drive roller is wound at a different position from the first tension roller; and a moving mechanism connected to the second tension roller to move the second tension roller in directions closer to and away from the endless belt. A range of adjustment of a circumferential length of the endless belt by the moving mechanism is larger than a range of adjustment of the circumferential length of the endless belt by the biasing mechanism.