An injection aid is a tool used by being attached to an injection device having an injection needle and a syringe, and includes an aid main body and a tapered guide. The aid main body includes an engagement part to be engaged with the syringe a hollow part through which the injection needle penetrates and a needle-protruding surface from which a needle tip part of the injection needle protrudes and which is brought into contact with skin when sticking the injection needle into a living body. The tapered guide is arranged in the hollow part of the aid main body and includes an inner surface that becomes continuously reduced in diameter toward the needle-protruding surface.
