A spark plug comprising: a generally cylindrical ceramic insulator including an axial bore extending along an axial line, a front end side step portion whose diameter tapering from a rear end side to a front end side and a tapered rear end side step portion positioned at the rear end side with respect to the front end side step portion and whose diameter tapering from the front end side to the rear end side, both the front end side step portion and the rear end side step portion formed on an outer circumferential face of the ceramic insulator; a generally cylindrical metal shell including a step portion that is formed on an inner circumferential face thereof and engaged with the front end side step portion of the ceramic insulator from the rear end side and a crimp portion that is formed in a rear end portion of the metal shell and crimped so that the rear end side step portion of the ceramic insulator is crimped from the rear end side, the metal shell fitted to the outer circumferential face of the ceramic insulator, characterized in that an area defined by an outer edge of the rear end side step portion and an inner edge of the crimp portion falls within a range of 5 mm 2 to 25 mm 2 when the spark plug is projected on a plane perpendicular to the axial line, an angle (θ1) formed by a tapered face of the rear end side step portion and a plane perpendicular to the axial line falls within a range of 20 degrees to 60 degrees, and a distance along the axial line from a front end of a proximal portion of the crimp portion to a frontmost position of a contact portion between an inner face of the crimp portion and the rear end side step portion falls within a range of 0.4 mm to 1.8 mm. a generally cylindrical ceramic insulator including an axial bore extending along an axial line, a front end side step portion whose diameter tapering from a rear end side to a front end side and a tapered rear end side step portion positioned at the rear end side with respect to the front end side step portion and whose diameter tapering from the front end side to the rear end side, both the front end side step portion and the rear end side step portion formed on an outer circumferential face of the ceramic insulator; a generally cylindrical metal shell including a step portion that is formed on an inner circumferential face thereof and engaged with the front end side step portion of the ceramic insulator from the rear end side and a crimp portion that is formed in a rear end portion of the metal shell and crimped so that the rear end side step portion of the ceramic insulator is crimped from the rear end side, the metal shell fitted to the outer circumferential face of the ceramic insulator, characterized in that an area defined by an outer edge of the rear end side step portion and an inner edge of the crimp portion falls within a range of 5 mm 2 to 25 mm 2 when the spark plug is projected on a plane perpendicular to the axial line, an angle (θ1) formed by a tapered face of the rear end side step portion and a plane perpendicular to the axial line falls within a range of 20 degrees to 60 degrees, and a distance along the axial line from a front end of a proximal portion of the crimp portion to a frontmost position of a contact portion between an inner face of the crimp portion and the rear end side step portion falls within a range of 0.4 mm to 1.8 mm.