The present invention relates to a blood-collecting needle having a variable length and provided with pain, inflammation, and risk prevention functions and, more particularly, to a blood-collecting needle in which, when a disposable blood-collecting needle is inserted into a semiautomatic blood collection device to collect blood, the blood-collecting needle not only reduces pain, but achieves perfect sanitation to relieve the sense of danger and anxiety felt by a user, and the length of the blood-collecting needle is freely changed in multiple stages. According to the present invention, a multi-bump disposed on a lower end of a main body may smoothly pass through a needle passage of the blood collection device to reduce pain while instantly contacting the peripheral epidermis during self-injection. The multi-bump may sanitarily collect blood while blocking the needle passage of the blood collection device. Also, the length of the blood-collecting needle may be freely changed in an optimal state according to various conditions by means of a simple method in which the multi-bump is cut in multiple stages.
