A lens array optical system includes a first lens array that includes plural first lens cells arranged in first and second directions, the first lens array being configured to split a light flux to plural split light fluxes and to condense each split flux; and a second lens array that includes plural second lens cells arranged in the first and second directions, each second lens cell being configured to receive the split lights from each first lens cell, wherein a ratio between a width of an arrangement area of the first lens cells and a width of an arrangement area of the second lens cells in the first direction is different from a ratio between a width of an arrangement area of the first lens cells and a width of an arrangement area of the second lens cells in the second direction, and wherein at least one of the first and second lens arrays has a toric surface.