A position specifying section obtains an observation distance by specifying the position of an irradiated region from a picked-up image that is obtained from the image pickup of a subject on which the irradiated region is formed by auxiliary measurement light. An image processing section sets the amount of offset, which corresponds to a height of the irradiated region of a convex portion of the subject, for the observation distance, and generates an offset measurement marker on the basis of the offset distance that obtained by adding the amount of offset to the observation distance. A specific image in which the offset measurement marker is superimposed on the picked-up image is displayed on a display unit.
