An illumination optical device has the following elements. A first optical block includes a first lens array having a plurality of cell lenses each being approximately similar in shape to a light modulation device. A second optical block includes a second lens array having a plurality of cell lenses corresponding to the respective cell lenses of the first lens array of the first optical block and each being approximately similar in shape to the light modulation device, and a first converging component for converging beams that have passed through the second lens array toward the light modulation device. A second converging component is disposed in the vicinity of the light modulation device and serves to image beams that are output from the second optical block at a predetermined position. The cell lenses of the first lens array have different aspherical surfaces.