Diaphragm valve

A diaphragm valve comprising:

• a body provided with a fluid channel and a depression opening upward;
• a seat arranged in a circumferential edge of the fluid channel formed in the body;
• an elastically-deformable, spherical shell-shaped diaphragm that opens and closes the fluid channel by being pressed against and separated from the seat;
• a pressing adaptor that retains an outer circumferential edge portion of the diaphragm between a bottom surface of the depression of the body and itself;
• a diaphragm presser that moves up and down and presses a central portion of the diaphragm, wherein
• in the pressing adaptor, a whole lower surface thereof has a taper shape at a predetermined inclination angle,
• the bottom surface of the depression of the 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, and
• in the diaphragm, in a state where the fluid channel is opened, an upper surface of the outer circumferential edge portion comes into surface contact with the taper-shaped lower surface 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.