A guide device having a guide body including a bearing surface designed to bear in a glenoidal cavity of a scapula that has been prepared beforehand, the guide body including at least one through orifice emerging in the bearing surface, a reference member mounted on the guide body and including a bearing portion designed to bear on the anterior cortex of the scapula, and adjustment means arranged to adjust the position of the reference member with respect to the guide body so as to adjust the distance between the bearing portion and an axis of the through orifice.
