An external screw member comprising a head , and a shank extending linearly from said head , said shank having a parallel threaded portion and a tapered threaded portion formed in order from said head toward a tip end, a screw thread being continuously formed on said parallel threaded portion and said tapered threaded portion at the same pitch, and said screw thread in said tapered threaded portion being configured in a form in which the height of a crest thereof becomes gradually smaller, wherein a convex portion (4; 14; 24) protruding more radially outward than the crest of said screw thread is formed in a part of the screw thread and in at least one of said parallel threaded portion and said tapered threaded portion over said tapered threaded portion and said parallel threaded portion ; a screw driving side end face (4d; 14d; 24d) of said convex portion (4; 14; 24) is configured to form an inclined plane which gradually rises from a root position of said end face (4d; 14d; 24d) at the side of the crest of said screw thread toward a crest (4a; 14a; 24a) of said convex portion (4; 14; 24) in a direction (W2) opposite to a screw driving direction (W1) of said screw thread to reach the crest (4a; 14a; 24a) of said convex portion (4; 14; 24) wherein the convex portion is provided with a convex crest extending a predetermined length along the screw thread crest of the screw thread , a pressure side convex flank extending from this convex crest toward a thread bottom at the side of the head , and a clearance side convex flank extending from the convex crest toward a thread bottom at the side of a screw tip, wherein a crest width of the convex crest is larger than the crest width of the screw thread crest , and the pressure side convex flank and the clearance side convex flank protrude more in the crest width direction at the side of the convex crest than the pressure side flank and the clearance side flank of the screw thread . wherein a convex portion (4; 14; 24) protruding more radially outward than the crest of said screw thread is formed in a part of the screw thread and in at least one of said parallel threaded portion and said tapered threaded portion over said tapered threaded portion and said parallel threaded portion ; a screw driving side end face (4d; 14d; 24d) of said convex portion (4; 14; 24) is configured to form an inclined plane which gradually rises from a root position of said end face (4d; 14d; 24d) at the side of the crest of said screw thread toward a crest (4a; 14a; 24a) of said convex portion (4; 14; 24) in a direction (W2) opposite to a screw driving direction (W1) of said screw thread to reach the crest (4a; 14a; 24a) of said convex portion (4; 14; 24) wherein the convex portion is provided with a convex crest extending a predetermined length along the screw thread crest of the screw thread , a pressure side convex flank extending from this convex crest toward a thread bottom at the side of the head , and a clearance side convex flank extending from the convex crest toward a thread bottom at the side of a screw tip, wherein a crest width of the convex crest is larger than the crest width of the screw thread crest , and the pressure side convex flank and the clearance side convex flank protrude more in the crest width direction at the side of the convex crest than the pressure side flank and the clearance side flank of the screw thread . <EOS>