An imaging device includes a pixel unit where pixels including photoelectric converters are arranged, and a signal processing unit that processes signals from the pixel unit. The pixel unit includes a first region including pixels each driven in a first mode to read a signal based on charge generated by the photoelectric converters and a second region including the pixels each driven in a second mode to read more signals than in the first mode including a signal based on charges generated by a part of the photoelectric converters and a signal based on charges generated by the photoelectric converters. The signal processing unit calculates a first correction value based on an average of a first data group from the first region and a second correction value based on an average of a second data group from the second region by using the first correction value as an initial value.