The coherent noise appears in the constructed image of digital holographic microscopy due to the laser source; thus, the imaging quality is degraded. A method of coherent noise reduction using a laterally shifting hologram aperture is presented. An original hologram with coherent noise is captured by a camera first. A series of holograms are sampled by laterally shifting the digital aperture in the original hologram. Instead of extracting the specimen’s part information, each sampled hologram, which includes the whole specimen, is reconstructed. The coherent noise is reduced by averaging the different reconstructed images. The experiment demonstrates the feasibility of the approach. The presented approach with a single recorded hologram realizes the coherent noise reduction without loss of spatial resolution, which is useful for real-time measurement.