A two-dimensional code reader and program generate edge images based on obtained images, extract candidate regions within these edge images, determine whether or not the extracted candidate regions are valid, determine whether or not characteristic patterns are included in each corresponding region in the original image, and then detects two-dimensional code regions within original images. The two-dimensional code reader and program repeatedly implement generation of edge images based on conversion conditions that correspond to the applicable order among a plurality of conversion condition types in a pre-set order, detection of candidate regions among the generated edge images, determination of whether or not the extracted candidate regions are valid, determination of whether or not characteristic patterns are included in the corresponding regions in the original images that correspond to valid candidate regions, and detection of two-dimensional code regions.