1. An object detecting device comprising: a comparing unit to extract feature amounts for two regions on a determining object image and compare a feature based on the two feature amounts extracted with a threshold; a computing unit to select one of two values having different absolute values according to said comparison result, and compute an evaluation value to determine whether or not an object is included in said determining object image, by performing computation with the selected value; and a determining information storage unit to store determining information including a plurality of combinations of two positions on said determining object image, said threshold, and said two values, wherein said comparing unit compares the two extracted features amounts for the two regions on said determining object image identified by said two positions, and said threshold, for each of said combinations, and wherein said computing unit selects one of said two values according to said comparison results and computes said evaluation values by sequentially performing computations of the selected values, for each of said combinations.