An apparatus (1) for forming an absorbent pad for an absorbent sanitary article comprising a first layer, a second layer and an absorbent material interposed between the first and the second layer, comprises: a forming drum (2)； a first feed system (4) for feeding to the forming drum (2) a first web (NW1), intended to form the first layer (101)； and a second feed system (5) for feeding to the forming drum (2) a second web (NW2), intended to form the second layer (102)； at least one spreader (6) for spreading the absorbent material (103) on the forming drum (2)； the first web (NW1), the second web (NW2) and the absorbent material (103) together form a composite web (NW) and the forming apparatus (1) comprises a system (10) for joining the first and second webs (NW1, NW2) and a system (20) for calibrating the thickness of the absorbent material (103) in the composite web (NW) and being located upstream of the joining system (10) in a feed direction V of the composite web.
