Although human activities in the World Wide Web are increasing rapidly due to the advent of many online services and applications, we still need to appraise how things such as a merchandise in a store or pictures in a museum receive attention in the real world. To measure people's attention in the physical world, we propose SPAL, a Sensor of Physical-world Attention using Laser scanning. It is challenging to use a laser scanner because it provides only front-side circumference of any detected objects in a measurement area. Unlike cameras, a laser scanner poses no privacy problem because it does not recognize and record an individual. SPAL includes many important factors when calculating people's attention, i.e., lingering time, direction of people, distance to a target object. To obtain such information for calculation, we develop three processing modules to extract information from raw data measured by a laser scanner. We define two attention metrics and two measurement models to compute people's attention. To validate the proposed system, we implemented a prototype of SPAL and conducted experiments in the real-world environment. The results show that the proposed system is a good candidate for determining people's attention.