An information processing device includes a detection unit and a calculation unit. The detection unit detects, as a measurement use point, a portion that is used for prescribed length measurement of the object, in each of sectioned regions, in an object image included in the photographed image, set on both sides with respect to a reference line which is set for the object image and by which the object image is sectioned. The calculation unit calculates the length of a segment, in each of the sectioned regions, between the measurement use point and the intersection point between the reference line and a perpendicular line passing through the measurement use point and being perpendicular to the reference line. Further, the calculation unit calculates a length, in the object, to be measured, by adding together the calculated lengths of the segments.