An optical switching device including a substrate and at least an organic film as a light control part formed on the substrate. Optical switching is performed by applying signal light and control light to the organic film, the wavelengths of the signal light and the control light being set in a region in the vicinity of resonance on the longer wavelength side in the absorption spectrum of the organic film; and by changing a real part or real and imaginary parts of the refractive index of the light control part by using the control light, to thereby cause a phase difference in the signal light.