An electronic device includes a first housing; a second housing slidable into and out of the first housing; a sliding plate configured to be at least partially slid within the second housing; a flexible display including a display area that is variable as the second housing slides into and out of the first housing; a printed circuit board in an inner space of the first housing; a first shaft; and a thermal diffusion member including a first end, disposed on the at least one electronic component and partially wound, and a second end coupled to the first shaft, and the thermal diffusion member is configured such that at least a portion of the thermal diffusion member spreads out in an inner space of the second housing as a sliding-out operation is performed by the second housing with respect to the first housing.