A load supporting structure of an electric booster type brake apparatus, includes: a housing including a rear housing member and a front housing member so as to define a receiving space therein; a ball screw shaft rotatably installed in the receiving space of the housing; a rotor installed at one side of the ball screw shaft so as to transmit torque; a first bearing installed between the rear housing member and one side of the rotor and configured to support a radial direction load due to a hydraulic reaction force; and a second bearing installed between the front housing member and the other side of the rotor and configured to support an axial direction load due to a hydraulic reaction force. Therefore, the number of components and the thickness of the housing are reduced, and therefore weight reduction of the electric booster type brake apparatus may be implemented.