A robot should make an adequate global path to offer smooth services to users. For this purpose, accurate environmental information, i.e. map, and continual map updating is needed. In this paper, we suggest a method of map updating for a global path planning of a robot. In this method, we first define the process of creating of map update factors. And then, a step for usage of map update factors is shown. Using this method, a robot can perform its mission with reduction of task load which is needed for collision avoidance in complex environment.