Abstract: An auxiliary positioning device is secured on a pedestal grinder which contains a transmission seat including a rotatable fixing block, an output shaft, and multiple grinding units. The auxiliary positioning device includes a support unit and at least one movable holding unit, wherein the support unit has a fitting orifice, a locking portion, and at least one coupling orifice. The locking portion has a slot and a locating portion, and a first of multiple screws is inserted through the slot from the locating portion to force the support unit relative to the rotatable fixing block, thus adjusting a tilting angle of the support unit relative to the rotatable fixing block. Two second of the multiple screws are inserted through the at least one coupling orifice so as to lock the at least one movable holding unit, thus positioning a workpiece auxiliarily.