1. An image processing apparatus, comprising: fluorescent image obtaining means for obtaining a fluorescent image by imaging fluorescence emitted by substances within blood vessels when an excitation light beam is irradiated onto the blood vessels; spectral image obtaining means for obtaining a plurality of spectral images, each of a different wavelength range, of the same blood vessels of which the fluorescent image is obtained; depth position judging means for judging the depth position at which the blood vessels exist, employing the plurality of spectral images obtained by the spectral image obtaining means; and image processing means for changing image processing conditions according to the depth position of the blood vessels judged by the depth position judging means, and administering a blood vessel emphasizing process on the fluorescent image.