A calibrator calibrates optical characteristics of an optical measurement apparatus in water by inserting a measurement probe connected to the optical measurement apparatus into the calibrator. The optical measurement apparatus is configured to perform optical measurement on body tissue. The calibrator includes: an accommodation portion that has an opening at one end thereof and accommodates the water, a distal end of the measurement probe being configured to be inserted into the accommodation portion and a removing unit that is arranged in the water and is configured to remove a substance adhered to the distal end of the measurement probe inserted into the accommodation portion.
