A method for controlling a wire electric discharge machine that performs machining of a workpiece in a work tank, the wire electric discharge machine including: a workpiece fixing unit (11; 21; 32) disposed in the work tank and including a movable axis to which the workpiece is detachably attached; a machining-reference-part detecting unit (12; 22; 31) for detecting a position of a machining reference part of the workpiece detachably fixed to the workpiece fixing unit (11; 21; 32), wherein the machining-reference-part detecting unit (12; 22; 31) is a vision sensor; and a machining-reference-part measuring unit (15; 26; 35) for measuring an error with respect to an ideal shape of the machining reference part of the workpiece detachably fixed to the workpiece fixing unit (11; 21; 32); wherein the method is characterized in that: the movable axis is controlled on the basis of position information of the machining reference part detected by the machining reference-part detecting unit (12; 22; 31), and a position of the machining reference part is positioned in a predetermined position; the machining-reference-part measuring unit (15; 26; 35) is positioned in a predetermined measurement position; and a measurement of the machining reference part of the workpiece is executed with the machining-reference-part measuring unit (15; 26; 35), wherein the execution of the positioning of the workpiece is effected by determining, from the position of the machining reference part detected by the machining-reference-part detecting unit (12; 22; 31) and the predetermined measurement position of the machining-reference-part measuring unit (15; 26; 35), whether the machining reference part and the machining-reference-part measuring unit (15; 26; 35) collide with each other, and when the machining reference part and the machining-reference-part measuring unit (15; 26; 35) are determined to collide with each other, the workpiece is positioned in a position where the machining reference part does not collide with the machining-reference-part measuring unit (15; 26; 35). a workpiece fixing unit (11; 21; 32) disposed in the work tank and including a movable axis to which the workpiece is detachably attached; a machining-reference-part detecting unit (12; 22; 31) for detecting a position of a machining reference part of the workpiece detachably fixed to the workpiece fixing unit (11; 21; 32), wherein the machining-reference-part detecting unit (12; 22; 31) is a vision sensor; and a machining-reference-part measuring unit (15; 26; 35) for measuring an error with respect to an ideal shape of the machining reference part of the workpiece detachably fixed to the workpiece fixing unit (11; 21; 32); wherein the method is characterized in that: the movable axis is controlled on the basis of position information of the machining reference part detected by the machining reference-part detecting unit (12; 22; 31), and a position of the machining reference part is positioned in a predetermined position; the machining-reference-part measuring unit (15; 26; 35) is positioned in a predetermined measurement position; and a measurement of the machining reference part of the workpiece is executed with the machining-reference-part measuring unit (15; 26; 35), wherein the execution of the positioning of the workpiece is effected by determining, from the position of the machining reference part detected by the machining-reference-part detecting unit (12; 22; 31) and the predetermined measurement position of the machining-reference-part measuring unit (15; 26; 35), whether the machining reference part and the machining-reference-part measuring unit (15; 26; 35) collide with each other, and when the machining reference part and the machining-reference-part measuring unit (15; 26; 35) are determined to collide with each other, the workpiece is positioned in a position where the machining reference part does not collide with the machining-reference-part measuring unit (15; 26; 35). the movable axis is controlled on the basis of position information of the machining reference part detected by the machining reference-part detecting unit (12; 22; 31), and a position of the machining reference part is positioned in a predetermined position; the machining-reference-part measuring unit (15; 26; 35) is positioned in a predetermined measurement position; and a measurement of the machining reference part of the workpiece is executed with the machining-reference-part measuring unit (15; 26; 35), wherein the execution of the positioning of the workpiece is effected by determining, from the position of the machining reference part detected by the machining-reference-part detecting unit (12; 22; 31) and the predetermined measurement position of the machining-reference-part measuring unit (15; 26; 35), whether the machining reference part and the machining-reference-part measuring unit (15; 26; 35) collide with each other, and when the machining reference part and the machining-reference-part measuring unit (15; 26; 35) are determined to collide with each other, the workpiece is positioned in a position where the machining reference part does not collide with the machining-reference-part measuring unit (15; 26; 35).