Abstract: Disclosed is a sleep induction device which exhibits excellent hypnotic effects using light rather than ultrasonic waves or electrical voltages to induce sleep. When the face of a patient is irradiated with diffused ultra narrow band light having a FWHM of 10 nm or less, the specified wavelength of light has excellent hypnotic effects. The sleep induction device is provided with: an ultra narrow band light irradiation means which generates a blue to green ultra narrow band light having a FWHM of 10 nm or less and a peak wavelength range of 430-550 nm; and a diffusion means for reducing the illumination intensity of the light irradiated from the ultra narrow band light irradiation means onto the skin surface of the face to 1-300 lux, and expanding the emission area to the entire face. The green ultra narrow band light has a sleep-inducing effect, and the blue one has a stronger sleep-inducing effect.