1. An image processing apparatus (a) used in an image capturing apparatus including a display unit and (b) configured to perform a process for displaying a still image acquired by the image capturing apparatus during its panning to follow a moving main object, the image processing apparatus comprising at least one processor or circuit configured to perform operations of the following units: a vector acquiring unit configured to acquire, from multiple motion vectors detected at multiple positions in a moving image acquired by the image capturing apparatus during the panning, a background motion vector corresponding to a background object different from the main object; and a processing unit configured (a) to determine, using the background motion vector, a background area of the still image where the background object is captured and (b) to perform a magnification display process for magnifying the background area as compared with a case where the display unit displays the entire still image and causing the display unit to display the magnified background area.