Abstract: An strain measuring apparatus for analyzing the stability of a steel structure and a method thereof employs a controller for receiving a variation difference amount from the strain gauge input unit measured using a strain gauge between a strain degree obtained by applying a weight to a steel structure and a strain degree obtained by applying a weight to a steel structure having a hole formed at a predetermined portion and measuring a strain existing in the steel structure based on the variation amount using particular equations. A control command input unit inputs an initialization command for initialing the existing strain measuring apparatus, a radius of the hole formed in the steel structure, a distance between the center of the hole and the center of the strain gauge attached to the steel structurc and an external operating signal including a proceeding command which represents a testing procedure into the controller.