Abstract: Provided is a micro-electro-mechanical system and an electro-acoustic conversion device having the micro-electro-mechanical system. The micro-electro-mechanical system includes: first and second membranes arranged opposite to each other; support members arranged between the first and second membranes; and an opening provided on the first and/or second membranes. Each support member includes support walls, and opposite ends of each of the support walls are connected to the first and second membranes. The first and second membranes, and two adjacent support walls in one support member are enclosed to form a first chamber. The opening is configured to link the first chamber with the outside. By arranging a supporting member composed of support walls and providing an opening on the first and/or second membranes, the compliance of the first or second membrane is increased, and the inter-plate capacitance therebetween is reduced.