Provided is an underwater mask including buckle with which a strap can be moved and adjusted in the up-down direction and the lateral direction on a wearers head. Buckle (15) are configured to couple a strap (16) to a mask body (14). The buckle each include a base (28) including a spring (37) with a locking hook (38), a strap adjuster body (30) turnably attached to the base and including a plurality of engaging teeth configured to sequentially engage with the locking hook according to the turn, a handling member (32) held inside the body and operated from outside the body, and a stopper (31) held by the body. The handling member includes a spring (64), sliding portion (66), and a pair of finger pads (65) exposed outside the body by the spring. The stopper includes a sliding contact tapered protrusion (58) having a function of, by the operation of the handling member, sliding against the pair of sliding portion to cause the stopper to swing toward a direction opposite to the strap adjuster body and releasing the engagement of the pawl with the engaging teeth of the strap.
