A slider for slide fastener comprising: a body; and a cover member supported on a front-side post section and a rear-side post section which are erected on an upper surface of the body, wherein the cover member comprises: a top plate; a pair of right and left side plates which extend downward from both side edges of the top plate; pull-tab receiving recesses which are respectively formed in the pair of right and left side plates and receive a shaft portion of a pull-tab; a hook which enters an element guide path of the body through a hook hole (2 1 a) formed in the body; an elastic piece which extends forward from a front end portion of the top plate, a leading end of the elastic piece being bent downward; a pair of right and left front-side engagement pieces which respectively extend forward from front end portions of the pair of right and left side plates and engage with the front-side post section; a pair of right and left rear-side engagement pieces which extend rearward from rear end portions of the pair of right and left side plates and engage with the rear-side post section; a concavely-shaped elastic piece receiving portion which is formed in a front surface of the front-side post section, the elastic piece receiving portion receiving the elastic piece; front-side engagement recesses which are respectively formed in right and left side surfaces of the front-side post section, the front-side engagement recesses having surfaces which face upper surfaces of the front-side engagement pieces; and rear-side engagement recesses which are respectively formed in right and left side surfaces of the rear-side post section, the rear-side engagement recesses having surfaces which face upper surfaces of the rear-side engagement pieces, characterized in that the front-side and rear-side engagement recesses are formed so as to penetrate in a front-rear direction of the body. a body; and a cover member supported on a front-side post section and a rear-side post section which are erected on an upper surface of the body, wherein the cover member comprises: a top plate; a pair of right and left side plates which extend downward from both side edges of the top plate; pull-tab receiving recesses which are respectively formed in the pair of right and left side plates and receive a shaft portion of a pull-tab; a hook which enters an element guide path of the body through a hook hole (2 1 a) formed in the body; an elastic piece which extends forward from a front end portion of the top plate, a leading end of the elastic piece being bent downward; a pair of right and left front-side engagement pieces which respectively extend forward from front end portions of the pair of right and left side plates and engage with the front-side post section; a pair of right and left rear-side engagement pieces which extend rearward from rear end portions of the pair of right and left side plates and engage with the rear-side post section; a concavely-shaped elastic piece receiving portion which is formed in a front surface of the front-side post section, the elastic piece receiving portion receiving the elastic piece; front-side engagement recesses which are respectively formed in right and left side surfaces of the front-side post section, the front-side engagement recesses having surfaces which face upper surfaces of the front-side engagement pieces; and rear-side engagement recesses which are respectively formed in right and left side surfaces of the rear-side post section, the rear-side engagement recesses having surfaces which face upper surfaces of the rear-side engagement pieces, characterized in that the front-side and rear-side engagement recesses are formed so as to penetrate in a front-rear direction of the body. a top plate; a pair of right and left side plates which extend downward from both side edges of the top plate; pull-tab receiving recesses which are respectively formed in the pair of right and left side plates and receive a shaft portion of a pull-tab; a hook which enters an element guide path of the body through a hook hole (2 1 a) formed in the body; an elastic piece which extends forward from a front end portion of the top plate, a leading end of the elastic piece being bent downward; a pair of right and left front-side engagement pieces which respectively extend forward from front end portions of the pair of right and left side plates and engage with the front-side post section; a pair of right and left rear-side engagement pieces which extend rearward from rear end portions of the pair of right and left side plates and engage with the rear-side post section; a concavely-shaped elastic piece receiving portion which is formed in a front surface of the front-side post section, the elastic piece receiving portion receiving the elastic piece; front-side engagement recesses which are respectively formed in right and left side surfaces of the front-side post section, the front-side engagement recesses having surfaces which face upper surfaces of the front-side engagement pieces; and rear-side engagement recesses which are respectively formed in right and left side surfaces of the rear-side post section, the rear-side engagement recesses having surfaces which face upper surfaces of the rear-side engagement pieces, characterized in that the front-side and rear-side engagement recesses are formed so as to penetrate in a front-rear direction of the body.