The present invention is to provide a head strap device which includes a head strap having a first set of connecting section, a second set of connecting section, and a central section, and an adjustment buckle for positioning and adjusting the head strap, characterized in that: the central section of the head strap is a curved surface that can be naturally approach engagement on a back of the head while worn to avoid the head strap sliding, in addition, an opening disposed within a body of the adjustment buckle, and a pins and a guide posts disposed with misaligned each other on the opening that can separate the overlapping head strap after assembled, so that there is no need to remove the swimming goggles when the head strap is worn and adjusted, to achieve the effect of easily use.