Provided is a diaphragm valve that can improve durability when the diaphragm valve is downsized. In a pressing adaptor, a whole lower surface thereof has a taper shape at a predetermined inclination angle. A bottom surface of a depression of a body has a circular flat portion and a depression that is continued to an outer circumference of the flat portion and is depressed with respect to the flat portion. In a diaphragm, in a state where a fluid inflow channel is opened, an upper surface of an outer circumferential edge portion comes into surface contact with the taper-shaped lower surface a of the pressing adaptor, and a lower surface of the outer circumferential edge portion comes into line contact with the outer circumference of the flat portion of the bottom surface of the depression of the body.