A syringe for treating facial wrinkles having a syringe cylinder, a needle body detachably mounted at the front end portion of the syringe cylinder and having a syringe needle disposed thereon, and a piston rod disposed inside the syringe cylinder for operating a piston is provided. The syringe includes: the syringe cylinder formed of a substantially thin tube having an inside diameter in a range of 2.0 mm to 7.0 mm; and an inflow check valve disposed at one side of the front end portion of the syringe cylinder so as to supply a predetermined quantity of gas to the interior of the syringe cylinder. The predetermined quantity of gas supplied through the inflow check valve to the interior of the syringe cylinder and a predetermined quantity of liquid filled into the syringe cylinder are injected in turn into the dermis of the skin, which is repeatedly carried out.