A blood information measuring apparatus comprising: a lighting section for applying illumination light to an internal body portion including a blood vessel; an imaging section for receiving reflection light from the internal body portion illuminated with the illumination light, and outputting an image signal; a wavelength band switching section for switching among wavelength bands of the illumination light to be applied to the internal body portion or of the reflection light to be incident on the imaging section such that two or more types of narrowband light constituting a designated wavelength set are applied or received successively, the two or more types of the narrowband light penetrating to similar depths into the internal body portion; a wavelength band switching controller for controlling the wavelength band switching section to automatically and successively switch the designated wavelength set among the wavelength sets such that the application of the illumination light or the receipt of the reflection light of each of the wavelength sets is carried out for given number of repetitions; and a blood information calculation section for calculating blood information of blood in the blood vessel based on the image signal, wherein the blood information is an oxygen saturation level of hemoglobin calculated based on absorbance, characterized in that the apparatus further includes a location detecting section for detecting a location of the internal body portion, wherein the wavelength band switching controller is configured to determine the number of repetitions of application of each of the wavelength sets based on the location detected. a lighting section for applying illumination light to an internal body portion including a blood vessel; an imaging section for receiving reflection light from the internal body portion illuminated with the illumination light, and outputting an image signal; a wavelength band switching section for switching among wavelength bands of the illumination light to be applied to the internal body portion or of the reflection light to be incident on the imaging section such that two or more types of narrowband light constituting a designated wavelength set are applied or received successively, the two or more types of the narrowband light penetrating to similar depths into the internal body portion; a wavelength band switching controller for controlling the wavelength band switching section to automatically and successively switch the designated wavelength set among the wavelength sets such that the application of the illumination light or the receipt of the reflection light of each of the wavelength sets is carried out for given number of repetitions; and a blood information calculation section for calculating blood information of blood in the blood vessel based on the image signal, wherein the blood information is an oxygen saturation level of hemoglobin calculated based on absorbance, characterized in that the apparatus further includes a location detecting section for detecting a location of the internal body portion, wherein the wavelength band switching controller is configured to determine the number of repetitions of application of each of the wavelength sets based on the location detected.