A circuit for auto-focus adjustment includes a calculating unit configured to calculate an indicator of randomness of pixel values in a captured image, a direction determining unit configured to compare a first value of the indicator calculated by the calculating unit in a preceding focus adjustment process with a second value of the indicator calculated by the calculating unit after the calculation of the first value, thereby to determine a direction of focus shift in response to a result of the comparison, and a control unit configured to start a focus adjustment process by which a focus position is first moved in the direction of focus shift determined by the direction determining unit.