A image restoration based on deconvolution method is proposed in digital holographic microscopy. To overcome the resolution limit of the optical imaging system, we applied two key concepts: image resizing and PSF (Point Spread Function) upscaling. This method provides detailed and extended frequency components to improve the quality of the image. We demonstrated the digital holographic microscopy system with the proposed image restoration and evaluated its performance. As a result, we confirmed that the proposed method is quite promising for realizing high quality images.