A mined material transport vehicle, comprising: a vehicle main body capable of moving forward and rearward; and a loading platform provided on the vehicle main body, wherein the loading platform comprises: a conveyor provided on the vehicle main body and having a conveying surface capable of conveying a mined material in a conveying direction extending in forward-rearward directions of the vehicle main body; a pair of movable flaps extending in the conveying direction on both sides of the conveying surface in a vehicle width direction, forming a storage space together with the conveying surface, and being rotatable about an axial line extending in the conveying direction between a first and a second position; a drive unit configured to rotate the movable flaps about the axial line; wherein the loading platform further comprises front fixed guides provided on both sides in the vehicle width direction in a front portion of the conveying surface, the front fixed guides extend upward toward an outer side in the vehicle width direction, and a front end of the movable flaps is positioned at an outer side in the vehicle width direction of a rear end of the front fixed guides in the second position when the movable flaps are rotated about the axial line toward the outer side in the vehicle width direction characterized in that the front portions of the pair of front fixed guides extend toward the front end so as to approach each other toward an inner side in the vehicle width direction, in planar view, and the first position is a position where the front end of the movable flap is continuous with the rear end of the front fixed guide. a vehicle main body capable of moving forward and rearward; and a loading platform provided on the vehicle main body, wherein the loading platform comprises: a conveyor provided on the vehicle main body and having a conveying surface capable of conveying a mined material in a conveying direction extending in forward-rearward directions of the vehicle main body; a pair of movable flaps extending in the conveying direction on both sides of the conveying surface in a vehicle width direction, forming a storage space together with the conveying surface, and being rotatable about an axial line extending in the conveying direction between a first and a second position; a drive unit configured to rotate the movable flaps about the axial line; wherein the loading platform further comprises front fixed guides provided on both sides in the vehicle width direction in a front portion of the conveying surface, the front fixed guides extend upward toward an outer side in the vehicle width direction, and a front end of the movable flaps is positioned at an outer side in the vehicle width direction of a rear end of the front fixed guides in the second position when the movable flaps are rotated about the axial line toward the outer side in the vehicle width direction characterized in that the front portions of the pair of front fixed guides extend toward the front end so as to approach each other toward an inner side in the vehicle width direction, in planar view, and the first position is a position where the front end of the movable flap is continuous with the rear end of the front fixed guide. a conveyor provided on the vehicle main body and having a conveying surface capable of conveying a mined material in a conveying direction extending in forward-rearward directions of the vehicle main body; a pair of movable flaps extending in the conveying direction on both sides of the conveying surface in a vehicle width direction, forming a storage space together with the conveying surface, and being rotatable about an axial line extending in the conveying direction between a first and a second position; a drive unit configured to rotate the movable flaps about the axial line; wherein the loading platform further comprises front fixed guides provided on both sides in the vehicle width direction in a front portion of the conveying surface, the front fixed guides extend upward toward an outer side in the vehicle width direction, and a front end of the movable flaps is positioned at an outer side in the vehicle width direction of a rear end of the front fixed guides in the second position when the movable flaps are rotated about the axial line toward the outer side in the vehicle width direction characterized in that the front portions of the pair of front fixed guides extend toward the front end so as to approach each other toward an inner side in the vehicle width direction, in planar view, and the first position is a position where the front end of the movable flap is continuous with the rear end of the front fixed guide.