A capsule-type medical device comprises a capsule main unit having functions for being inserted into the body cavity and performing medical acts such as taking images or the like. The capsule main unit comprises therein a magnet which is acted upon by external magnetism, and a spiral portion on the outer perimeter, so that rotating force acting upon the magnet is readily converted into a propelling force for propelling the capsule-type medical device. A flexible insertion portion which is long and small in diameter is provided to the capsule main unit to allow smooth progression through the body cavity, and the center of gravity of the device is placed upon the longitudinal center axis of the capsule main unit, thus facilitating smooth progression through the body cavity.