Abstract: A medical capsule having an outer cylinder and a piston movable in the outer cylinder, the piston being activated by an externally given signal so as to discharge a medicine to the outside of the capsule or to suck a humor for a sampling purpose, as well as an apparatus for activating this medical capsule. The capsule has a remote-controllable means including a normally-opened lead switch which connects a power supply to an activating means in response to an externally given magnetic signal thereby initiating activation of the medical capsule, whereby a simple medical capsule which is operative with minimized electrical power consumption without affecting the living body can be obtained. The activating apparatus has a pair of magnetic field generating units arranged side-by-side so as to generate magnetic lines of force in various directions and to form magnetic fields covering a large area, thus ensuring correct activation of the medical capsule inside the living body.