A blood-vessel recognizing method for recognizing blood vessels present in biological tissue, the method including: obtaining real-time Doppler spectra on the basis of time waveforms data of intensities of scattered light generated in the biological tissue due to irradiation with laser light； calculating average frequencies of the real-time Doppler spectra； correcting the calculated average frequencies on the basis of peak intensities of the real-time Doppler spectra； and determining whether or not blood vessels are present in regions of the biological tissue irradiated with the laser light on the basis of the corrected average frequencies.
