A method for deploying an external air bag, including searching region of a front of vehicle, updating a physical amount of a searched object within the searching region each measurement period of a front sensor, determining a predicted physical amount each unit time during each measurement period, and predicting the physical amount by assuming that a specific searched object is moved at a constant speed when a capture of the specific searched object which was searched by the front sensor is stopped, selecting a target object among searched objects based on a relative speed or an overlap of the searched object obtained by the updating step or (Time To External Airbag) TTE and deploying the external air bag in a case in which each of a relative speed and an overlap predicted when the target object collides are a predetermined level or more.