The image processing device according to one embodiment of this disclosure comprises an extraction unit which extracts a feature quantity included in a captured image and an object discrimination unit which discriminates an object on the basis of the feature quantity. The extraction unit executes convolution operation through use of a filter having a plurality of filter values in a two-dimensional arrangement on the basis of the captured image to extract the feature quantity. The plurality of filter values in the filter are set to values line-symmetrical about a symmetry axis along a predetermined direction.