PROBLEM TO BE SOLVED: To provide an automatic injection device which is small in size and has a low-profile shape, thereby allows a walking patient to conveniently handle the device to be able to inject a medical solution, or the like, into the skin of a patient for a long term, and has a basic design to be simply and inexpensively manufactured.SOLUTION: This device 20 for delivering a liquid therapeutic preparation into the body of the patient by injection into or through the skin of the patient comprises a low-profile housing having a bottom surface 24 adapted to be brought into contact with the skin of the patient. A reservoir is disposed within the housing for containing the liquid therapeutic preparation to be administered. An injection needle is carried by a movable needle carrier which is disposed in the housing. The injection needle has a bent injection end which is adapted to project through a needle aperture in the bottom surface of the housing. The height of the housing is minimized. As a result, the housing is sufficiently low in height to allow the device to be worn inconspicuously under the clothing of the patient.