An injection needle safety instrument used as being assembled to a barrel of a syringe, the injection needle safety instrument comprising: a base portion including a fixed portion fixed to the barrel of the syringe; a cover portion including an accommodation portion which can cover a pointed end of a needle tube included in an injection needle by accommodating the pointed end of the needle tube attached to a front end portion of the syringe; and a hinge portion which pivotably couples the base portion and the cover portion to each other, the hinge portion having a pivot axis extending in a direction orthogonal to an axial line of the barrel, the base portion being provided with a locking portion, the cover portion being provided with a first locked portion locked to the locking portion and a second locked portion locked to the injection needle, the cover portion being constructed to be pivotable between a first position at which the pointed end of the needle tube is exposed as the cover portion is arranged on a side of a rear end portion of the barrel relative to the pivot axis of the hinge portion along a direction of the axial line of the barrel and the cover portion is held to the base portion as the locking portion locks the first locked portion and a second position at which the cover portion covers the pointed end of the needle tube as the cover portion is arranged on a side of the pointed end of the needle tube relative to the pivot axis of the hinge portion along the direction of the axial line of the barrel and the cover portion is held to the injection needle as the injection needle locks the second locked portion, and the cover portion being located as being tilted such that the cover portion comes closer to the barrel from a side of a base end which is a side where the hinge portion is located toward a tip end which is a side where the hinge portion is not located while the cover portion is arranged in the first position and being arranged in the second position as the cover portion pivots by an angle beyond 180° around the pivot axis of the hinge portion. a base portion including a fixed portion fixed to the barrel of the syringe; a cover portion including an accommodation portion which can cover a pointed end of a needle tube included in an injection needle by accommodating the pointed end of the needle tube attached to a front end portion of the syringe; and a hinge portion which pivotably couples the base portion and the cover portion to each other, the hinge portion having a pivot axis extending in a direction orthogonal to an axial line of the barrel, the base portion being provided with a locking portion, the cover portion being provided with a first locked portion locked to the locking portion and a second locked portion locked to the injection needle, the cover portion being constructed to be pivotable between a first position at which the pointed end of the needle tube is exposed as the cover portion is arranged on a side of a rear end portion of the barrel relative to the pivot axis of the hinge portion along a direction of the axial line of the barrel and the cover portion is held to the base portion as the locking portion locks the first locked portion and a second position at which the cover portion covers the pointed end of the needle tube as the cover portion is arranged on a side of the pointed end of the needle tube relative to the pivot axis of the hinge portion along the direction of the axial line of the barrel and the cover portion is held to the injection needle as the injection needle locks the second locked portion, and the cover portion being located as being tilted such that the cover portion comes closer to the barrel from a side of a base end which is a side where the hinge portion is located toward a tip end which is a side where the hinge portion is not located while the cover portion is arranged in the first position and being arranged in the second position as the cover portion pivots by an angle beyond 180° around the pivot axis of the hinge portion.