The present invention relates to a needle unit for injecting liquids such as medicine or tattooing pigment spread to a skin, into the skin, and a dermatological liquid injection apparatus using the same. The present invention includes a body unit including a driving device, a cam member rotated by the driving device, and a connecting member reciprocally driven by the cam member； a needle unit detachably mounted to a front end of the body unit； and a rubber member installed to the needle unit, for blocking blood and liquid mixture which are discharged from a skin of a patient and flow into the needle unit, from flowing to the body unit during a medical procedure.
