In a traditional lensless in-line holographic microscope (LIHM), the field of view (FOV) is generally limited by the size of the imaging sensor, which is usually several millimeters wide. We propose a scanning LIHM system using a line-scan camera to achieve wide field-of-view holographic imaging. In addition, the iterative holographic reconstruction method is applied to obtain the sample image with enhanced contrast and resolution using two hologram measurements, which are acquired by slightly shifting the sample-to-sensor distance. The capability of the proposed scanning LIHM system was demonstrated by experiments with a U.S. Air Force target and a biological sample of leaf vein. The reconstructed sample image had a FOV of 2.87  cm  ×  4.70  cm (2048  ×  3357  pixels), which was much larger than the typical FOV of several square millimeters in a traditional LIHM system.