An object of the invention is to securely capture a group of continuous in-vivo images in which at least parts of image portions overlap between in-vivo images. An in-vivo observing system 1 of the invention includes a capsule endoscope 2 introduced into a body of a subject, a magnetic field generating unit 3 for generating external magnetic fields to the capsule endoscope 2 in the subject, and a control unit 11 for controlling the magnetic field generating unit 3. The capsule endoscope 2 includes an illuminating unit for illuminating a body of the subject by illumination light and an imaging unit for sequentially capturing in-vivo images of the subject illuminated by the illuminating unit. The control unit 11 causes the magnetic field generating unit 3 to change magnetic field directions of the external magnetic fields at an angular speed less than a multiplied value of a frame rate and an angle of view of the imaging unit and causes the magnetic field generating unit 3 to change an image capturing direction of the capsule endoscope 2 following the magnetic field directions at this angular speed.
