A medical guidance system and a control method of a medical device are provided, which may increase the drive force of a medical device and improve controllability thereof. The medical guidance system has a medical device that includes a biologic information acquisition unit that acquires biologic information of the inside of a body cavity and a magnet that generates drive force in response to a magnetic field exerted from the outside of a body, a magnetic field generation unit 101 that generates the magnetic field to be exerted on the magnet from the outside of a body, and a displacement detection unit 105 that detects displacement being an angle formed between the magnetization direction of the magnet and the field direction of the magnetic field generated by the magnetic field generation unit 101 at the position of the medical device; wherein the magnetic field generation unit 101 is controlled based on the displacement.