The invention provides a head stack assembly manufacturing device and provides a step of adhering an auxiliary suspension mounting slide block which is assembled with an E block. But in the step of adhering the auxiliary suspension mounting slide block which is assembled with the E block, because a force which is applied in the loading direction of an HGA single body by means of an adhering member when a slide block is loaded on the HGA single body, arrangement of a fixed base which alleviates HGA flexure is difficult. The head stack assembly manufacturing device is provided with the slide block which is loaded on the loading surface of a flexible member that is provided with a load bending part, and testure of the flexible member is controlled by a plate-shaped bearing member which is supported by the E block of the head stack assembly. The head stack assembly manufacturing device is characterized by comprising a bearing beam supporting part which alleviates HGA flexure through the force in the loading direction in loading of the slide block. Through the characteristic, damage of the adhering member can be promoted and loading time is shortened.