Disclosed is an injector for an animal having a marking liquid jetting part, the injector comprising: a fixing body part (100) in which an operation rod (120) for moving a piston (330) forward or backward is provided in a hollow portion of a main housing (110)； a pressing part (200) for pressing the operation rod (120) when a medicinal liquid is injected； a medicinal liquid injecting part (300) for injecting the medicinal liquid, which fills a medicinal liquid room (321), into animals through a needle portion (310) by the pressing of the piston (330)； and a marking liquid jetting part (400) for jetting a disinfectant or a color liquid to an external side of the skin of the animal. Here, the marking liquid jetting part (400) includes an auxiliary housing (410), an operating element case (430), a front pressing element (450), and a second elastic body (470). The auxiliary housing (410) forms a second hollow portion (411) by auxiliary housing elements (410a, 410b) fixed to the main housing (100). A marking liquid storage case (P1) is inserted into the operating element case (430). The operating element case (430) is positioned in the auxiliary housing (410) to be able to slide. While retreating by a second distance (D2), the operating element case (430) presses the marking liquid storage case (P1), thereby frontward extruding the marking liquid in the marking liquid storage case (P1). While retreating by a first distance (D1) longer than the retreat distance of the operating element case (430) by a blow applied to the skin of the animal, the front pressing element (450) allows the operating element case (430) to retreat by a second distance (D2) = (1/20-1/2)×；D1 at the time of initial retreat. A front side of the second elastic body (470) is connected to the front pressing element (450) and a rear side of the second elastic body (470) is supported by the auxiliary housing (410), thereby providing the force of restitution to the front pressing element (450).피스톤(330
