A female coupler and a male coupler of a pipe coupling that are easy to assemble and have a minimized passage resistance are provided. The female coupler includes a cylindrical female coupler body adapted to receive the male coupler from a front end opening thereof. A pipe connection adapter has a cylindrical connecting portion that is inserted into the female coupler body from a rear end opening thereof, and is thus connected to the female coupler body. The pipe connection adapter has two support legs extending from the front end surface of the cylindrical connecting portion. A valve support ring is secured to the distal ends of the support legs. The valve support ring has an outer circumferential surface that has a diameter smaller than the outer diameter of the cylindrical connecting portion, whereby a fluid passage is defined between the outer circumferential surface of the support ring and the wall surface of the through-hole of the female coupler body. The support legs are connected to the valve support ring at the rear end surface thereof. The male coupler has an arrangement similar to the above.