Abstract: Disclosed in the present specification is an image processing method performed by an image processing device, the image processing method comprising the steps of: obtaining a first image representing a 2D image of 3D content observed from a first position in a 3D coordinate system and a second image representing a 2D image of the 3D content observed from a second position in the 3D coordinate system; detecting a first boundary line representing one boundary of the 3D content from the first image; detecting a second boundary line representing the one boundary from the second image; and determining a third boundary line for three-dimensionally expressing the one boundary in the 3D coordinate system using the first boundary line and second boundary line.