An acoustic output device includes a base case whose internal space is formed as an arrangement space and in which an insertion hole communicating with the internal space is formed, a cover that covers at least a part of the base case, an elastically deformable waterproof sheet including a flat surface portion joined to the base case and a bag-shaped pocket portion inserted into the insertion hole, a push button including an operating portion to be pressed and operated and a working portion inserted into the pocket portion, a substrate that is arranged in the arrangement space, and a switch that is arranged on the substrate and operated by the working portion via the pocket portion.