1. A method of analyzing a hazard of an elevator software control system by a computer, the method comprising: determining an attribute and function demands of the elevator software control system; analyzing tasks of the elevator software control system based on the determined attribute and the function demands; generating specification of a relation between the tasks using Concur Task Tree (CTT) method, the CTT method representing a hierarchical relation of a control flow between the tasks; and determining at least one of the hazard of the elevator software control system based on the specification, wherein the determining at least one of the hazard of the elevator software control system uses a guide word mapping table of CTT based System Theoretic Process Analysis (STPA), and wherein the structure of the elevator software control system is divided into an internal part and an external part; the external part of the elevator software control system includes a summon button to summon an elevator and the summon button includes an up button and a down button; and the internal part of the elevator software control system includes a car where passengers board and a door, and a floor request button, an open button and a close button are disposed in the car.