A display module and a display device are provided. The display module includes a display panel and a composite layer. The composite layer is located on a backlight side of the display panel and includes a heat dissipation layer. The display panel includes a planar region, curved regions and corner regions. The curved regions are partially arranged around the planar region and the corner regions are disposed at corners of the curved regions. In one corner region, the heat dissipation layer includes at least one opening. The corner region includes a first position and a second position. A width of the opening at the first position is smaller than the width of the opening. At the half length of the opening, the width D2 of the opening is smaller than half of the maximum width D1 of the opening.