The invention provides a medical guiding system including: a position data calculating device for detecting position and orientation of an ultrasonic endoscope serving as a medical instrument; image storing section for storing medical image data obtained before use of the ultrasonic endoscope; a body position correcting section for correcting at least one of position and direction at least one of viscera and organ in the medical image data, in line with a body position of the subject; and an image configuring section for calculating a position of the ultrasonic endoscope in the medical image data corrected by body position correcting section, based on a position of the ultrasonic endoscope obtained by the position data calculating device.