Abstract: A disposable mask for dust protection is provided for maintaining contact with the wearer's face even when moving one's mouth, in which the strap is fixed to maintain tension, and to enable easy adjustment of the length of the strap. The disposable dust protective mask includes a filter body having a front filter, upper and lower sealing wings coupled to the front filter such that they can fold which closely contact the ridge of the nose and the jaw of the wearer, first spread-guiding lines, formed at respective sides corresponding to the front filter, for guiding the upper and lower sealing wings to be spread, second spread-guiding lines for guiding the upper and lower sealing wings to be spread, strap adjusting devices coupled to both sides of the filter body, and a strap connected to the strap adjusting devices and hung on the wearer. The upper and lower sealing wings spread apart along the first and second spread-guiding lines depending on movement of the wearer's mouth and jaw.