A roller shade apparatus for a vehicle includes a shade sheet placed selectively in wound-up and extended states, the wound-up state being established to uncover a light transmitting member mounted to the vehicle when the shade sheet is moved in an opening direction, the extended state being established to shield the light transmitting member when the shade sheet is moved in a closing direction, a pair of guide rails extending in the opening and closing directions, and guide belts slidably supported by respective guide portions of the guide rails along the opening and closing directions and connected to respective side end portions of the shade sheet, wherein each guide belt curved in the width direction includes a convex surface, a central portion of the convex surface is connected to each side end portion, and each guide portion includes a pair of lock portions locking side portions of the guide belt.