To provide a diaphragm pump for a fluid which has a small number of components, is easy to assemble, has low noise and is excellent in stability and reliability of an open/close valve.

The diaphragm pump for a fluid includes a motor 15, a crank base 13, a shaft member 14, an oscillating plate 12, a diaphragm assembly 3, a case member 11, a retainer member 2, an inner lid 4, an intake valve film assembly 5, and an upper lid 6. The inner lid includes: a through-hole coupled with the retainer member, forming a pump chamber by bringing a diaphragm into tight contact and capable of communication from the outside of the pump chamber; a discharge hole 46 from which a fluid in the pump chamber is discharged upward as a volume of the pump chamber decreases; and a cylindrical intake valve seat protruding upward from the vicinity of the through-hole. An outer peripheral surface of the intake valve seat has a tapered surface which narrows upward.