Disclosed herein is a method of constructing an environmental map using sonar sensors. The method includes the steps of checking whether conflict cells have occurred using input sonar sensor data; if conflict cells have occurred, selecting incorrect data and eliminating the conflict cells using sound pressure comparison until the conflict cells do not occur any longer; and once the elimination has completed, preparing a grid map using a Maximum Approximated Likelihood (MAL) approach. Inconsistency in data occurs when multiple pieces of sensor data overlap each other, the conflict cells are cells that experience inconsistency over an entire arc region, and candidates for the incorrect sonar sensor data are obtained when the conflict cells occur.