To securely position a needle tip and a blade face of a needle tube inserted into the skin in a predetermined site of a living body, such as the upper layer of skin, an injection needle assembly includes a needle tube having a needle tip capable of puncturing a living body, a hub holding the needle tube, a stabilizer, and a guide portion. The stabilizer is formed in a tubular shape surrounding the circumference of the needle tube, and an end face is pressed against the skin, and thereby a raised portion of the skin is formed in a tube hole. The guide portion is arranged on the stabilizer, and is adapted to recognize a press-in distance y of the stabilizer to the skin.