Disclosed are an object detection method and a convolution neural network. The method is performed through hierarchical architecture of the CNN and includes extracting groups of augmented feature maps from an input image through a backbone and two other groups of feature maps, identifying positive and negative samples with an IOU-based sampling scheme to be proposals for foreground and background through a proposal-sampling classifier, mapping the proposals to regions on the groups of augmented feature maps through the region proposal module, pooling the regions to fixed scale feature maps based on ROI aligning, fusing the fixed scale feature maps, and flattening the fused feature maps to generate an ROI feature vector through an ROI aligner for object classification and box regression. Because extracted features in the groups of augmented feature maps range from spatially-rich features to semantically-rich features, enhanced performance in object classification and box regression can be secured.