A mattress includes a layer including a first surface and a second surface arranged opposite to the first surface. The layer defines a plurality of slits extending from the first surface to the second surface and arranged in a plurality of rows extending in a longitudinal direction. The slits in each row are arrayed linearly in the longitudinal direction and are disposed spaced apart from each other. The rows of the slits restrict a compression of the layer to an area under loading and prevent the surrounding portion of the layer from being pulled towards the area under loading.