An invisible zipper head assembly structure includes a sliding member and a pulling member. The sliding member has a base portion, a first lateral wall portion, a second lateral wall portion, a seat portion, and a retaining body. The retaining body has a positioning portion passing through a positioning through hole of the seat portion. The pulling member is movably mated with the retaining body. A first thickness of the first lateral wall portion is smaller than a second thickness of the second lateral wall portion. The first symmetric center line of the base portion passes through a geometric center point of the positioning through hole, and the second symmetric center line of the seat portion is horizontally moved relative to the first symmetric center line by a predetermined horizontal offset and along a horizontal direction from the second lateral wall portion to the first lateral wall portion.