A method of measuring fat thickness in a target, the method comprising: radiating near infrared rays having a first wavelength at a fat sample, measuring an absorptance of the fat sample with respect to the near infrared rays having the first wavelength (720, 730), measuring a thickness of the fat sample using an ultrasonic wave, and generating an equation defining a relationship between the absorptance obtained at the first wavelength and the fat thickness; generating and radiating near infrared rays having the first wavelength at the target, receiving light reflected from the target in response to the near infrared rays, and calculating a ratio of intensity of the light reflected from the target to intensity of the near infrared rays radiated at the target to obtain absorptance of the target with respect to the near infrared rays having the first wavelength; and calculating the fat thickness in the target using the calculated absorptance and the generated equation, wherein the method is characterized in that the step of radiating further comprises radiating near infrared rays having a second wavelength at the fat sample and measuring an absorptance of the fat sample with respect to the near infrared rays having the second wavelength, the equation defining a relationship between the absorptances respectively obtained at the first and second wavelengths and the fat thickness, wherein the step of generating further comprises generating and radiating near infrared rays having the second wavelength at the target, and calculating a ratio of intensity of the light reflected from the target to intensity of the near infrared rays radiated at the target to obtain absorptance of the target with respect to the near infrared rays having the second wavelength; and wherein the step of calculating comprises calculating the fat thickness in the target using the two calculated absorptances and the generated equation, and wherein the first and second wavelengths are 930 nm and 1040 nm, respectively. radiating near infrared rays having a first wavelength at a fat sample, measuring an absorptance of the fat sample with respect to the near infrared rays having the first wavelength (720, 730), measuring a thickness of the fat sample using an ultrasonic wave, and generating an equation defining a relationship between the absorptance obtained at the first wavelength and the fat thickness; generating and radiating near infrared rays having the first wavelength at the target, receiving light reflected from the target in response to the near infrared rays, and calculating a ratio of intensity of the light reflected from the target to intensity of the near infrared rays radiated at the target to obtain absorptance of the target with respect to the near infrared rays having the first wavelength; and calculating the fat thickness in the target using the calculated absorptance and the generated equation, wherein the method is characterized in that the step of radiating further comprises radiating near infrared rays having a second wavelength at the fat sample and measuring an absorptance of the fat sample with respect to the near infrared rays having the second wavelength, the equation defining a relationship between the absorptances respectively obtained at the first and second wavelengths and the fat thickness, wherein the step of generating further comprises generating and radiating near infrared rays having the second wavelength at the target, and calculating a ratio of intensity of the light reflected from the target to intensity of the near infrared rays radiated at the target to obtain absorptance of the target with respect to the near infrared rays having the second wavelength; and wherein the step of calculating comprises calculating the fat thickness in the target using the two calculated absorptances and the generated equation, and wherein the first and second wavelengths are 930 nm and 1040 nm, respectively.