A contour detecting device, including: a display; and a processor, wherein the processor obtains a detection target image which is obtained by imaging a detection target, detects a contour of the detection target from the detection target image by performing shape recognition a plurality of times, the shape recognition recognizing a shape of the contour of the detection target, and causes the display to display a detection result of contour detection processing, and in the contour detection processing, for feature points forming contours obtained by performing the shape recognition the plurality of times, variance in the shape recognition that is performed the plurality of times is calculated for each corresponding feature points, and a feature point for which a value of the calculated variance is a set value or greater is determined to be a feature point which has a low reliability.