The present invention provides a slider with a simple locking mechanism which allows the slider to be operated easily and exerts its locking function accurately. In the slider of this invention, a recess is made in the center of an upper wing plate of a slider body thereof and engaging posts are provided on the front and back of the slider body. Two pawl holes are provided in a bottom portion of the recess and supporting pieces are provided on the right and left sides so as to be erected. Guide grooves are provided in side walls of the recess. A pawl body comprises locking pawls provided on the right and left of a bottom face thereof in which a top face thereof is formed in a mountain shape and their phases are deviated by half pitch and guide protruding portions protruding from the side walls. A pull tab has a pintle on an end thereof and a cam is provided in the center of the pintle. A cover is a rectangular prism and has front and rear engaging holes which are capable of engaging the engaging posts. The guide protruding portions of the pawl body are inserted into the guide grooves of the recess and the pull tab is placed on the supporting pieces from above. Then, the cover is mounted. When the pull tab is raised or hung, the pawl body moves up and down, so that the locking pawls enter in between fastener elements by pressure.