An intense positron microprobe has been developed for obtaining three-dimensional positron lifetime mappings in a sample to permit visual evaluation of defect distributions. The beam diameter of an intense positron beam injected into the sample was 30 micrometers. Two-dimensional images at arbitrary depth were demonstrated of positron lifetimes in a fused silica sample, which was irradiated with ion beams. The time taken to obtain a single image was about 1 hour.