Disclosed is a four-wheeled folding handcart, including: a main body; and a loading plate provided with at least one loading plate wheel unit at a lower portion thereof, connected to the main body via a hinge unit such that the loading plate is folded by the hinge unit while being rotated toward the main body, and loading an article thereon. The loading plate wheel unit is connected to a wheel rod rotated by the rotation of the hinge unit in a direction perpendicular to a rotational direction of the hinge unit. The loading plate wheel unit is configured such that, when the loading plate is rotated and folded, the loading plate wheel unit is rotated and folded as the wheel rod rotates, and when the loading plate is rotated and unfolded, the loading plate wheel unit is rotated and unfolded as the wheel rod rotates reversely.