In the earlier research of reflective tomography laser imaging radar, only the silhouette image of the target rather than the image of the target plane can be reconstructed. An experiment of spotlight mode incoherently synthetic aperture imaging ladar is reported. With this method, the two-dimension image of the target plane is got. In the experiment, the angle-range-intensity data are collected in terms of the rotated side-looking incoherent projections of the target and the image is reconstructed by filtered back-projection algorithm. Computer simulation results is acquired as verification for the image reconstructed from experimental data. As a kind of incoherently synthetic aperture imaging ladar, this system has great practical significance for applications in extensive imaging fields.