An image forming apparatus includes at least first (202K), second (202C) and third image (202M) carriers (202M), a first drive source (98), a second drive source (99), at least one visible image forming mechanism for forming a visible image on the image carriers, a transfer unit (15) for overlappingly transferring the visible images, an image detector (136), and a controller (150). The first drive (98) source transmits a driving force to at least the first image carrier (202K). The second drive source (99) transmits a driving force to at least two image carriers other than the first image carrier (202K). The controller (150) calculates an amount of misalignment of the overlapped visible images that remain at the start timing of image formation based on the start timing of image formation after the timing correction, and separately determines driving speeds of the first (98) and the second drive sources (99) based on the amount of misalignment of the overlapped visible images.