The invention provides a forming method of a via hole, including: sequentially stacking a patterned first conductive layer, a first insulating layer, a patterned second conductive layer, and a second insulating layer on a substrate. The second conductive layer and the first conductive layer overlap in a normal direction of the substrate, such that the second insulating layer has a protrusion portion protruding away from the substrate. A photosensitive material layer covers the second insulating layer. The photosensitive material layer is exposed, wherein a depth of exposure is equal to a vertical distance from a top surface of the protrusion portion to a surface of the photosensitive material layer. The exposed photosensitive material layer is removed by development to form a first via hole exposing the second insulating layer. The exposed second insulating layer is etched to form a second via hole to expose the second conductive layer, and then the photosensitive material layer is removed. A manufacturing method of a pixel structure, using the forming method of the via hole, is also provided.