To provide an automatic transaction device, a customer detection method and a program for grasping the location of a user, and giving appropriate guidance by a left-untaken customer's medium alert or the like.

The automatic transaction device for automatically executing transaction on the basis of the operation of a customer includes: a detection part for detecting whether or not an object exists within a predetermined detection distance; an adjustment part for changing the detection distance in accordance with the detection result of the detection part; and a control part for making the adjustment part change the detection distance, and for making the detection part detect whether or not the object exists within the changed detection distance to grasp the motion of the object, and for grasping the motion of the customer.