A biological information detector includes a light-emitting part for emitting light in an emission wavelength band that includes a wavelength of interest, a light-receiving part for receiving light R1′ having biological information; a reflecting part for reflecting the light R1′ having the biological information at a reflecting surface towards the light-receiving part; and a filter for transmitting the wavelength of interest, the filter being provided between a detection site and the light-receiving part. The filter inhibits light in a wavelength band from a maximum wavelength of incident light to at least a maximum wavelength in the reception wavelength band, and the reflecting surface is configured so that only light having an angle of incidence that is equal to or less than the predetermined angle reaches the light-receiving part.