An imaging apparatus comprising: an image processing unit configured to generate a volume image of an object (ob) including a region of interest and extract a cross sectional image including the region of interest as a reference plane of the volume image automatically by using anatomical information including a feature point and a feature line of the object or manually by using a feature point or a feature line input from a user; and an area setting unit configured to set a vertical distance from the reference plane - by calculating a similarity between a cross sectional data of a region of interest contained in the reference plane and a cross sectional data of a region of interest contained in the plurality of cross sectional images, and setting a distance from the reference plane to a plurality of cross sectional images having a similarity greater than a reference value as the vertical distance from the reference plane or - by obtaining Doppler information of the region of interest contained in the plurality of cross sectional images, and setting a distance from the reference plane to a plurality of cross sectional images having color information of a region of interest, which is contained in Doppler information of the reference plane or indicating blood flow speed, which is contained in Doppler information, greater than a reference value as the vertical distance from the reference plane, wherein the image processing unit is configured to perform post-processing in the area set by said area setting unit. an image processing unit configured to generate a volume image of an object (ob) including a region of interest and extract a cross sectional image including the region of interest as a reference plane of the volume image automatically by using anatomical information including a feature point and a feature line of the object or manually by using a feature point or a feature line input from a user; and an area setting unit configured to set a vertical distance from the reference plane - by calculating a similarity between a cross sectional data of a region of interest contained in the reference plane and a cross sectional data of a region of interest contained in the plurality of cross sectional images, and setting a distance from the reference plane to a plurality of cross sectional images having a similarity greater than a reference value as the vertical distance from the reference plane or - by obtaining Doppler information of the region of interest contained in the plurality of cross sectional images, and setting a distance from the reference plane to a plurality of cross sectional images having color information of a region of interest, which is contained in Doppler information of the reference plane or indicating blood flow speed, which is contained in Doppler information, greater than a reference value as the vertical distance from the reference plane, - by calculating a similarity between a cross sectional data of a region of interest contained in the reference plane and a cross sectional data of a region of interest contained in the plurality of cross sectional images, and setting a distance from the reference plane to a plurality of cross sectional images having a similarity greater than a reference value as the vertical distance from the reference plane or - by obtaining Doppler information of the region of interest contained in the plurality of cross sectional images, and setting a distance from the reference plane to a plurality of cross sectional images having color information of a region of interest, which is contained in Doppler information of the reference plane or indicating blood flow speed, which is contained in Doppler information, greater than a reference value as the vertical distance from the reference plane, wherein the image processing unit is configured to perform post-processing in the area set by said area setting unit.