An object of the present invention is to easily stick an injection needle into a desired part in a subject without increase in the size of an apparatus. A body-insertable apparatus according to the present invention is an apparatus introduced into the subject and for injecting medical agent stored in casing into the desired part in the subject. The apparatus includes a plurality of injection needles (4a to 4c) for injecting medical agent into the desired part in the subject and a balloon (5) for projecting the plurality of injection needles (4a to 4c) from the casing (2). The balloon 5 projects the plurality of injection needles (4a to 4c) approximately at the same time by one driving source. The injection needles (4a to 4c) projected from the casing (2) pierce and/or push the wall of the alimentary tract in the subject, and fix the casing (2) to the desired part in the subject.
