Diagnosis using a flexible endoscope in gastro-intestinal tract becomes very important. In addition, the endoscope is a basic tool of diagnosis and treatment for digestive organ. However, the operation of endoscope is very labor intensive work and gives patients some pains. Therefore, the capsule-type endoscope is developed for the diagnosis of digestive organs. For its conveniences for diagnosis, the capsule endoscope comes into the spotlight. However, it is passively moved by the peristaltic waves of gastro-intestinal tract and thus has some limitations for doctor to get the image of the organ and to diagnose more thoroughly. In order to solve these problems, therefore, a locomotive mechanism of capsule endoscopes has being developed. For the locomotion in the gastro-intestinal tract, our proposed capsule-type microrobot has synchronized multiple legs that are actuated by a linear actuator and two mobile cylinders inside of the capsule. For the feasibility test of the proposed locomotive mechanism, a series of in-vitro experiments using small intestine without incision were carried out. In addition, in-vivo animal tests under a general anesthesia are also executed. From the experimental results, we conclude that the proposed locomotive mechanism is not only applicable to micro capsule endoscopes but also effective to advance inside of intestinal tract.