1. A reflection type oximeter comprising: beam source means including first to sixth beam sources (11 to 16) for emitting first to sixth beams and applying said beams to a living body tissue, wherein first and second beams have a wavelength involving a change in absorbance due to a change in an oxygen saturation of hemoglobin in blood of said body tissue, wherein third and fourth beams have another wavelength involving no change in absorbance, and wherein fifth and sixth beams have a further wavelength involving a relatively small change in absorbance due to changes in a quantity of hemoglobin and in an oxygen saturation, beam receiving means for detecting said first, second, third, fourth, fifth and sixth beams reflected from said tissue, wherein said first, third and fifth beam sources are located at positions distant from a center of said beam receiving means by a predetermined distance d1, and wherein said second, fourth and sixth beam sources are located at positions distant from the center of said beam receiving means by a predetermined distance d2, with a relation of d1&lt;d2 being maintained, evaluation means for evaluating intensities of said first, second, third, fourth, fifth and sixth beams reflected by said body tissue based on an output of said beam receiving means and for evaluating the quantity of hemoglobin in said body tissue based on a predetermined function, and output means (26, 27) for outputting results of the evaluation of said evaluating means.