An image sensor for detecting a wide spectrum includes a plurality of infrared ray receiving layers which individually receive infrared rays having different wavelengths for each pixel, the plurality of infrared ray receiving layers stacked to each other. The image sensor, which is an integrated image sensor where at least two micro bolometers are stacked, acquires spectrum information about visible rays and near-infrared rays as well as two or more infrared rays applied on an object, without mechanical/thermal/optical distortion, and provides the spectrum information to a silicon-based semiconductor such as a photodiode, thereby improving photoelectric conversion efficiency.