Auto-focusing device and image pickup device

An auto-focusing device comprising:

• an image sensor unit configured to generate image data by capturing a subject image formed on an imaging plane;
• an optical system which includes a focus lens and is configured to form the subject image on the imaging plane;
• a lens driver configured to drive the focus lens along an optical axis direction;
• a lens position detector configured to detect a position of the focus lens;
• a region detector configured to detect a predetermined region of the subject image in the image data;
• a processor configured to:
• calculate an AF evaluation value from the image data;
• and
• determine whether a subject is moving closer or away based on whether the predetermined region detected by the region detector has been enlarged or reduced from the predetermined region detected before;
• and
• a lens controller configured to control the lens driver, wherein
• the lens controller controls a moving direction and a moving speed of the focus lens in an autofocus operation based on the determination result provided from the processor, the AF evaluation value provided by the processor, and a position detection result for the focus lens provided by the lens position detector, and
• the lens controller changes the moving direction of the focus lens in the autofocus operation based on the determination result provided from the processor regarding whether the predetermined region detected by the region detector has been enlarged or reduced from the predetermined region detected before.