A photon-beam-position monitor (PBPM) was newly installed in a diagnostic beamline of the Pohang Light Source (PLS). We chose a blade-type PBPM to remove the thermal effect. The new PBPM was carefully designed to eliminate other error sources and was tested by using a high-power ultraviolet (UV) laser to check its performance before installation. The measurement result for the beam position showed that the thermal effect was reduced significantly. In addition, this result agreed well with data from the nearest beam position monitor (BPM) inside the PLS storage ring.