To surely control a medical system with a simple operation by performing the controlling of system through the provision of a recess or projection within an area of a projection face where an operation element is projected by a projector, and through the detection of position (movement) of operator's finger on the projection face by means of an optical detector.

An X-ray CT device has a gantry 2 supported with a base so as to be inclinable around a horizontal axis 1. and the gantry 2 has a measurement opening 3. The base holding the gantry 2 has two support columns 4, 5, and projection faces 6a-6d are provided on the front and rear surfaces of the columns 4, 5. The faces 6a-6d are arranged as projectors in correspondence with video beamers 7-10 hung from a ceiling in an inspection room. A video camera 12 is connected to a computing unit 11 so as to take an image of the projection face projecting an operation element at every time points, and with the image, operation data such as the inclination angle of the gantry 2, the position of bed, data of patients are obtained.