An automatic cardiopulmonary resuscitation device, comprising: a chest compressor which is movable, and is configured to repeatedly compress a victim's chest to a predetermined depth and in a predetermined cycle; wherein the automatic cardiopulmonary resuscitation device is adapted to adjust a compression site of the chest compressor by moving the chest compressor on the XY plane in the horizontal and vertical directions; and a cardiac output measurement unit configured to measure a cardiac output of the victim caused by compression of the chest compressor; and a processor configured to control the chest compressor to move according to a predetermined method, and to change the compression site, wherein the processor is configured to control the cardiac output measurement unit to measure the cardiac output of the victim at each of the changed compression sites, to select a compression site at which the cardiac output of the victim becomes the maximum, based on the measured cardiac output, and to control the chest compressor to move to the compression site at which the cardiac output of the victim becomes the maximum, characterized in that the predetermined method is a method which measures the cardiac output of the victim while moving the chest compressor in one direction of a horizontal direction or a vertical direction, selects a first compression site at which the cardiac output of the victim becomes the maximum, based on the measured cardiac output, and to move the chest compressor to a second compression site and a third compression site which are on both sides of the first compression site in a direction perpendicular to the moving direction of the chest compressor, and in that the processor is configured to select a compression site at which the cardiac output of the victim becomes the maximum as a final compression site, based on cardiac outputs measured at the first to third compression sites. a chest compressor which is movable, and is configured to repeatedly compress a victim's chest to a predetermined depth and in a predetermined cycle; wherein the automatic cardiopulmonary resuscitation device is adapted to adjust a compression site of the chest compressor by moving the chest compressor on the XY plane in the horizontal and vertical directions; and a cardiac output measurement unit configured to measure a cardiac output of the victim caused by compression of the chest compressor; and a processor configured to control the chest compressor to move according to a predetermined method, and to change the compression site, wherein the processor is configured to control the cardiac output measurement unit to measure the cardiac output of the victim at each of the changed compression sites, to select a compression site at which the cardiac output of the victim becomes the maximum, based on the measured cardiac output, and to control the chest compressor to move to the compression site at which the cardiac output of the victim becomes the maximum, characterized in that the predetermined method is a method which measures the cardiac output of the victim while moving the chest compressor in one direction of a horizontal direction or a vertical direction, selects a first compression site at which the cardiac output of the victim becomes the maximum, based on the measured cardiac output, and to move the chest compressor to a second compression site and a third compression site which are on both sides of the first compression site in a direction perpendicular to the moving direction of the chest compressor, and in that the processor is configured to select a compression site at which the cardiac output of the victim becomes the maximum as a final compression site, based on cardiac outputs measured at the first to third compression sites.