The present invention relates to a medicinal fluid injection device for injecting a medicinal fluid into the skin of a patient so as to induce collagen generation and skin regeneration according to the radial diffusion of the medicinal fluid, comprising: a case part constituting the appearance； a medicinal fluid placing part mounted on the case part and in which a storage container storing a medicinal fluid is mounted； a medicinal fluid supply part connected to the storage container so as to supply a medicinal fluid； a medicinal fluid pressurization part mounted on the case part, and connected to the medicinal fluid supply part so as to pressurize the supplied medicinal fluid； and a medicinal fluid discharge part mounted on the medicinal fluid supply part so as to inject, into the skin, the medicinal fluid supplied from the medicinal fluid supply part. The medicinal fluid discharge part comprises: an outer case in which a plurality of needles are provided； and an inner case provided such that the front end is inserted into the outer case so as to be coupled thereto and the rear end is coupled to the medicinal fluid supply part. A through hole penetrating the inside and the outside of the inner case and forming a micro-jet from the medicinal fluid is formed at the front end of the inner case.
