A method and apparatus for measuring fat thickness in a target body part are provided. The apparatus includes a light emitter emitting near infrared rays, an inner reflector having a reflecting plane outside to reflect the near infrared rays emitted by the light emitter, an outer reflector surrounding the inner reflector and having a reflecting plane inside to reflect the near infrared rays emitted by the light emitter, a light receiver receiving light reflected from the target body part in response to the near infrared rays, and a calculator calculating the fat thickness in the target body part using the light received by the light receiver.