A color image sensor has a white fluorescent tube as a light source, a microlens array with three rows of microlenses arranged vertically, a three-layer optical waveguide array and a three-line color CCD with color filters. The waveguides in each waveguide array layer are bent so that the interval between successive waveguides becomes narrower from the input end toward the output end. The three-line color CCD has three lines of light-receiving elements (photodiodes) as the light sensing portion. These lines in the light-receiving element array are arranged vertically at the same intervals as the waveguide layers are arranged. Further, a cylindrical lens is attached to cover the microlens array. Because of the presence of this cylindrical lens, the images of light beams incident on different microlenses of the microlens array corresponding to different waveguide layers are the same image from an identical area on the original.