Disclosed herein is a device for correcting golf swing posture. The device includes a footboard which is formed so that a foot is seated and supported thereon, and has a pair of facing locking brackets and a foot support part for supporting a foot. A support cuff is provided at an end of the footboard to support a leg, a lower surface of the support cuff, which contacts the footboard, being formed to be convex such that the support cuff rotates within a range of swing motion, the support cuff having locking recesses which are coupled to the locking brackets and a leg support part for supporting the leg. A fastening means detachably fastens the locking brackets of the footboard to the locking recesses of the support cuff. Thereby, the support cuff rotates about the fastening means at a predetermined angle as swing motion is conducted. Therefore, the support cuff can rotate relative to the footboard at a predetermined angle within the range of swing motion, so that the posture correction device can precisely correct swing posture, and can perfectly apply and support swing power, thus improving swing power, and making the ball fly in the desired direction, therefore improving golfing performance.