An image forming device and a color misregistration correction method allow for stable formation of excellent images with little color misregistration. A reference patch image is formed on a reference photosensitive drum 3, and transferred to a transfer belt 7. A correction patch image is formed on a correction-target photosensitive drum 3, and transferred onto the reference patch image by superimposition. A registration detecting sensor 21 detects a density average value of the reference patch image and the correction patch image. Based on the density average value, a correction value for controlling the correction-target photosensitive drum 3 is calculated, and rotational phase control is performed in accordance with the correction value.