The 3D obstacle sensor for Yamanote Line platform screen door is the sensor which considered safety in particular because of environmental resistance and an overcrowded railway based on the installation environment as the outside installation. In order to realize stable transport along the congested railway section and ensure the safety of customers, we have picked out points, which are [1] the maximal detection of risk factors, [2] using in outdoor environment, and [3] easiness of doing maintenance ; and we have formulated necessary specifications to realize the obstacle sensors for platform screen doors for the purpose of solving those points. In this report, the authors will describe the required specifications and software processing to realize the specifications.