A double shoulder tool joint comprising: a box comprising a box access sleeve including a first contact surface perpendicular to a pipe axis, a female threaded portion having a taper relative to the pipe axis, a box backward sleeve including a second contact surface perpendicular to the pipe axis; and a pin comprising a pin base including a third contact surface to contact the first contact surface, a male threaded portion to be screwed and engaged to the female threaded portion, a pin nose including a fourth contact surface perpendicular to the pipe axis to contact the second contact surface, wherein the double shoulder tool joint further comprises a guard portion (20, 30) including a fifth contact surface provided in a tip portion of the box extended forward from the first contact surface and a sixth contact surface provided in a tip portion of the pin extended forward from the fourth contact surface, wherein the sixth contact surface of the guard portion provided in the tip portion of the pin is configured to contact a seventh contact surface provided at a position extended backward from the second contact surface of the box backward sleeve, and wherein the dimensions of the contact surfaces of each of the box and the pin are configured such that the first contact surface and the third contact surface, the second contact surface and the fourth contact surface, and the sixth contact surface and the seventh contact surface contact successively with each other when the box and pin are engaged with each other by screwing the female threaded portion and the male threaded portion to provide threaded engagement. a box comprising a box access sleeve including a first contact surface perpendicular to a pipe axis, a female threaded portion having a taper relative to the pipe axis, a box backward sleeve including a second contact surface perpendicular to the pipe axis; and a pin comprising a pin base including a third contact surface to contact the first contact surface, a male threaded portion to be screwed and engaged to the female threaded portion, a pin nose including a fourth contact surface perpendicular to the pipe axis to contact the second contact surface, wherein the double shoulder tool joint further comprises a guard portion (20, 30) including a fifth contact surface provided in a tip portion of the box extended forward from the first contact surface and a sixth contact surface provided in a tip portion of the pin extended forward from the fourth contact surface, wherein the sixth contact surface of the guard portion provided in the tip portion of the pin is configured to contact a seventh contact surface provided at a position extended backward from the second contact surface of the box backward sleeve, and wherein the dimensions of the contact surfaces of each of the box and the pin are configured such that the first contact surface and the third contact surface, the second contact surface and the fourth contact surface, and the sixth contact surface and the seventh contact surface contact successively with each other when the box and pin are engaged with each other by screwing the female threaded portion and the male threaded portion to provide threaded engagement.