To provide swimming goggles with a head strap length adjustment mechanism which can easily perform connection operation and length adjustment of a head strap and prevent a locked state of the head strap from being released carelessly even in an attached state and an unattached state.SOLUTION: A length adjustment tool 10 includes a base member 20, a pair of sliders 50, 60 with both end parts 8A, 8B of a head strap 8 connected, respectively, and lock means for regulating movement of the pair of sliders 50, 60 in a state in which the pair of sliders 50, 60 are separated from each other. The movement of both end parts 8A, 8B of the head strap 8 is regulated in a state in which the sliders 50, 60 are locked, and locked states of the sliders 50, 60 and the head strap 8 are released by making the pair of sliders 50, 60 slide in the direction of coming closer to each other.SELECTED DRAWING: Figure 1