A CMOS image sensor of stack architecture is provided to increase the sensitivity by overcoming the limit of the photo diode capacity. A CMOS image sensor(100) of stack architecture comprises the first CMOS image sensor(120) and the second CMOS image sensor(140) welded by the stack architecture. The first CMOS image sensor and the second CMOS image sensor are welded by the medium of optical transmission adhesive part through which light can optically transmit. A mode control unit(160) controls the operation of the first and the second CMOS image sensors. The mode control unit selects one between the single action mode and the dual action mode. One sensor is operated in the single action mode among the first and the second CMOS image sensors. The first and the second CMOS image sensor are operated in the dual action mode.
