An optical measurement method suitable for measuring a distribution of lipid in a blood vessel and an optical probe suitable for use in such a method are provided. An optical probe 10 includes an optical fiber 11 for transmitting light between a proximal end 11a and a distal end 11b, an optical connecter 12 being connected to the optical fiber 11 at the proximal end 11 a, a focusing optical system 13 and a deflection optical system 14 each being connected to the optical fiber 11 at the distal end 11b, a support tube 15 and a jacket tube 16 each surrounding the optical fiber 11 to extend along the optical fiber 11, and a buffer fluid 17 filled in the inner lumen of the jacket tube. The optical fiber 11 has a cutoff wavelength shorter than 1.53 µm. The optical fiber 11, the focusing optical system 13, the deflection optical system 14, and the buffer fluid 17 and jacket tube 16 on an optical path coupled to a fundamental mode of the optical fiber each have the light transmittance of -2 dB to 0 dB in a wavelength band of 1.6 µm to 1.8 µm.
