The invention provides a mask belt adjuster, and belongs to the field of masks. The mask belt adjuster comprises a first clamping piece and a second clamping piece hinged to each other, wherein a first clamping port for clamping an ear belt is arranged at an end part of the first clamping piece; a second clamping port for clamping the ear belt is arranged at an end part of the second clamping piece has; an accommodating groove is formed in a part, close to the first clamping piece, of the second clamping piece; and the first clamping piece can be turned over and fall into the accommodating groove. The mask belt adjuster is matched with a mask for use, and can extend or shorten an overall length of the ear belt, so that the ear belt of the mask is more suitable for the head size of a wearer, and the mask can be more comfortably worn on the head of a user.