PROBLEM TO BE SOLVED: To generate appropriate endoscopic images suited to the purpose of a diagnosis even when an observation distance is changed corresponding to the purpose of the diagnosis.SOLUTION: Broadband light BB and narrow band light NB1 are simultaneously radiated to a subject. By imaging the subject by a color CCD, a blue signal B, a green signal G and a red signal R are obtained. From the signals, a base image is generated. It is defined as a near view state when the similarity of the blue signal B and the green signal G is low and as a distant view state when the similarity is high. In the near view state, a first color space indicating the relation of a ratio B/G, between the blue signal B and the green signal G, and a blood vessel depth is set. In the distant view state, a second color space indicating the relation of a ratio B/R, between the blue signal B and the red signal R, and the blood vessel depth is set. From the set color space and signals obtained by imaging the subject, blood vessel depth information is acquired. By reflecting the acquired blood vessel depth information on a base image, a blood vessel image including the blood vessel depth information is generated.
