1. An image taking apparatus which takes a first and a second images by using an image pickup device, comprising: a controller which detects a displacement amount of the second image with respect to the first image which is a reference image and performs predetermined processing at stages of pre-exposure for object observation and exposure for image taking; and a display unit which displays the first and the second images, wherein at the stage of pre-exposure for object observation, the controller determines regions to be displayed on the display unit in the first and the second images based on the displacement amount, and makes the display unit to display the images in the regions sequentially in predetermined periods, and at the stage of exposure for image taking, the controller synthesizes the first and the second images so that the second image conforms to the first image based on the displacement amount to generate a synthesized image whose exposure is corrected.