A gingivitis diagnosis assistance device (20A) is provided with a cross-section data extraction unit (21) for extracting cross-section data in a depth direction of a gingivitis peripheral part from three-dimensional point group data of a mouth front, and a gingivitis diagnosis data generating unit (25) for processing the cross-section data into a format suitable for gingivitis diagnosis and generating gingivitis diagnosis data, the gingivitis diagnosis data generating unit (25) generating, as the gingivitis diagnosis data, a two-dimensional graph in which the left-right direction or the up-down direction of the mouth front is the first axis and the depth direction is the second axis, for example.
