Abstract: A diaphragm valve 1 is provided with a body 2 having a flow-in passage 6, a flow-out passage 7, and a valve seat 8 formed between the passages; a diaphragm 3 installed in the body 2 and permitted to rest on and move away from the valve seat 8; and a driving means 4 installed on the body 2 to allow the diaphragm 3 to rest on and move away from the valve seat 8, wherein synthetic resin films 5 of predetermined thickness are coated on fluid-contacting parts 25 of the afore-mentioned body 2 and diaphragm 3. A diaphragm valve in accordance with the present invention prevents corrosion of the valve members caused by accumulation and adherence of substances produced by thermal decomposition, and prevents clogging caused by substances produced, and prevents seat leakage when applied in the vacuum exhaust system of a semiconductor manufacturing facility.