A field-programmable gate array (FPGA) coarse Hough transform unit (102) performs on an FPGA a first coarse-precision Hough transform upon an image that has been applied as input to an image input unit (101), and supplies candidate location information obtained by the first Hough transform and the image to an external memory (103). A fine Hough transform unit (104) reads the candidate location information and the image stored in the external memory (103), uses the candidate location information to perform, on a general-purpose processor, a second detailed-precision Hough transform upon the image, and supplies detailed-precision location information of a two-dimensional pattern that is the object of recognition within the image to the external memory (103).