To provide a pile driver and a centroid position measuring method for the pile driver with which a centroid position of the pile driver can be measured easily in a simple structure by integrating a sensor which detects a load in the pile driver per se.

As a leader bracket connection member for connecting an upper rotating body 15 and a leader bracket 18, four first pin-shaped load cells 23 are used for detecting loads, including a leader 16 and an auger driving device 29, applied to the leader bracket 18. The first pin-shaped load cells 23 are disposed above and under right and left side parts of the leader bracket 18, respectively. Mount holes 23a, 23b for mounting the upper first pin-shaped load cells 23 are formed circular correspondingly to a diameter of the first pin-shaped load cells 23, and lower mount holes 23c, 23d are formed in an elliptic shape which is elongated in a perpendicular direction with respect to the diameter of the first pin-shaped load cells 23.