A configuration detection device includes a light-providing optical fiber, a light reflector a curvature-detecting optical fiber, and a light modulator. The light-providing optical fiber transmits detection light in a plurality of wavelength ranges that have different wavelengths from one another, The light reflector reflects the detection light as reflected light. The curvature-detecting optical fiber transmits the reflected light, and is bent together with an endoscope. The light modulator modulates at least one of the strength or the wavelength of the reflected light for each of the wavelength ranges. Based on at least one of the strength or the wavelength of the reflected light that is pre-modulated and post-modulated, and based on the distance between the light modulator and the output end of the curvature-detecting optical fiber, the configuration of the endoscope is detectable.