Autofocus device has a lens-driving unit, a focal-point-position-detecting unit, and a distance measurement sensor that measures a distance to a subject. The device also has a control unit for controlling the lens-driving unit to drive the lens, thereby meeting the detected position of the focal point of the lens to an in-focus position. If a restart condition has not yet been satisfied after meeting the position of the focal point to the in-focus position to stop the focus operation, the control unit determines a switch of focusing on subjects based on the detected position of the focal point and a measured distance result by the distance measurement sensor and then restarts the focus operation based on a determination result thereof, thereby driving the lens to meet the position of the focal point to an in-focus position based on a measured distance result by the distance measurement sensor.