A hemoglobin concentration measuring system, comprising: a transvaginal probe (100, 300), the transvaginal probe (100, 300) including: an ultrasound transmitting/receiving part (103, 312) that is capable of transmitting ultrasound to living tissue and capable of receiving an ultrasound echo reflected from the living tissue; a light irradiation part (101, 323) that is capable of emitting light in a direction parallel to a scanning plane of the ultrasound transmitted from the ultrasound transmitting/receiving part (103, 312), wherein the light contains components of a plurality of specific wavelengths from a wavelength region ranging from visible light to near-infrared light; and a light receiving part (102, 324) that is capable of receiving reflected light or transmitted light, wherein the reflected light or the transmitted light is light emitted from the light irradiation part (101, 323) and reflected by or transmitted through the living tissue to propagate in a direction parallel to the scanning plane; a display part that is capable of displaying an ultrasound image containing an image of an ovarian cyst based on the ultrasound echo received by the ultrasound transmitting/receiving part (103, 312); and a concentration calculation part that calculates hemoglobin concentration in a cystic fluid retained in the ovarian cyst based on an optical spectrum of the reflected light or the transmitted light from the ovarian cyst received by the light receiving part (102, 324), wherein the concentration calculation part acquires absorbance measurement values at the plurality of specific wavelengths, and calculates the hemoglobin concentration by substituting the absorbance measurement values into a pre-acquired predetermined formula that represents the relationship between absorbance at the plurality of specific wavelengths and hemoglobin concentration, wherein the components of the plurality of wavelengths include, at least, components of a wavelength in a visible light region, and wherein the pre-acquired predetermined formula is a multiple regression formula constructed based on measurements using simulated cysts. a transvaginal probe (100, 300), the transvaginal probe (100, 300) including: an ultrasound transmitting/receiving part (103, 312) that is capable of transmitting ultrasound to living tissue and capable of receiving an ultrasound echo reflected from the living tissue; a light irradiation part (101, 323) that is capable of emitting light in a direction parallel to a scanning plane of the ultrasound transmitted from the ultrasound transmitting/receiving part (103, 312), wherein the light contains components of a plurality of specific wavelengths from a wavelength region ranging from visible light to near-infrared light; and a light receiving part (102, 324) that is capable of receiving reflected light or transmitted light, wherein the reflected light or the transmitted light is light emitted from the light irradiation part (101, 323) and reflected by or transmitted through the living tissue to propagate in a direction parallel to the scanning plane; an ultrasound transmitting/receiving part (103, 312) that is capable of transmitting ultrasound to living tissue and capable of receiving an ultrasound echo reflected from the living tissue; a light irradiation part (101, 323) that is capable of emitting light in a direction parallel to a scanning plane of the ultrasound transmitted from the ultrasound transmitting/receiving part (103, 312), wherein the light contains components of a plurality of specific wavelengths from a wavelength region ranging from visible light to near-infrared light; and a light receiving part (102, 324) that is capable of receiving reflected light or transmitted light, wherein the reflected light or the transmitted light is light emitted from the light irradiation part (101, 323) and reflected by or transmitted through the living tissue to propagate in a direction parallel to the scanning plane; a display part that is capable of displaying an ultrasound image containing an image of an ovarian cyst based on the ultrasound echo received by the ultrasound transmitting/receiving part (103, 312); and a concentration calculation part that calculates hemoglobin concentration in a cystic fluid retained in the ovarian cyst based on an optical spectrum of the reflected light or the transmitted light from the ovarian cyst received by the light receiving part (102, 324), wherein the concentration calculation part acquires absorbance measurement values at the plurality of specific wavelengths, and calculates the hemoglobin concentration by substituting the absorbance measurement values into a pre-acquired predetermined formula that represents the relationship between absorbance at the plurality of specific wavelengths and hemoglobin concentration, wherein the components of the plurality of wavelengths include, at least, components of a wavelength in a visible light region, and wherein the pre-acquired predetermined formula is a multiple regression formula constructed based on measurements using simulated cysts.