A push switch of the present disclosure has: a resin case that has a recess, a through hole, and a groove; a connection terminal; an upper protection sheet; and a lower protection sheet. The through hole penetrates from a bottom part of the recess to a lower surface of the resin case, and the groove is provided on the lower surface of the resin case. The through hole and the groove are connected to each other, and the through hole overlaps with the lower protection sheet in plan view. The groove has a first area and a second area, and of the first area and the second area, only the first area overlaps with the lower protection sheet in plan view.

A backlight module of an illuminated keyboard device includes a circuit board and a plurality of light-emitting elements. The circuit board has a top surface and a bottom surface opposite to the top surface. The top surface has a plurality of key assembling regions. Each of the key assembling regions has a stress release hole defined through the top surface and the bottom surface. The light-emitting elements are respectively disposed on the key assembling regions. Each of the light-emitting elements includes a main body and a conductive portion connected to the main body. The conductive portion is electrically connected to the circuit board, and the stress release hole is adjacent to the conductive portion of each of the light-emitting elements.