It is desired to provide technology that enables automatic measurement of the size of a subject with a reduced number of frames of images required, relaxed restrictions on the coverage and light projection, and no limitation on the shape of the subject. Provided is an information processing device including: a depth information acquiring unit configured to acquire depth information; a data conversion unit configured to convert the depth information into three-dimensional data; a subject extraction unit configured to extract a subject area where a subject is present on the basis of the three-dimensional data; and a size measurement unit configured to measure a size of the subject on the basis of the subject area, in which the size measurement unit detects six planes circumscribing the subject area and measures the size of the subject on the basis of the six planes.