There are provided an X-ray generating apparatus capable of switching X-ray beams of high energy and low energy to each other at high speed, and an X-ray CT apparatus capable of performing high-speed and high-quality multi-energy imaging by using the same. The X-ray generating apparatus is constructed by an X-ray tube 9 having two anodes 200a, 200b, a rotational anode 204 for radiating X-ray from an X-ray focal point by electron beams emitted from filaments of these cathodes, and two grid electrodes 202a and 202b for controlling emission of the electron beams, a tube voltage generator 9a and a tube voltage controller 9d1 for controlling an X-ray condition, a filament heater 9b and a tube current controller 9d2, a grid voltage generator 9c and a grid opening/closing controller 9d3, and a grid switching unit 9e. High energy X-ray and low energy X-ray are switched and emitted to an examinee every adjacent projection angles, thereby collecting projection data.