A female coupler suitable for use with a high pressure fluid is provided. The female coupler has locking members or balls adapted to be forced into engagement with a male coupler inserted into the female coupler by a sleeve or outer movable member. The sleeve is held by holding members or balls until the male coupler is inserted into the female coupler and a locking ball receiving recess formed in the exterior surface thereof is brought into a position for receiving the locking balls therein. Accordingly, the sleeve is prevented from moving to a position for forcing the locking ball into the locking ball receiving recess even if the male coupler is suddenly moved out from the female coupler, which is a problem that can occur in prior art female couplers. Further, the sleeve is provided with handle. An operator can grip the handle to hold the female coupler and align it with the male coupler, and advance the former towards the latter so that male coupler is inserted into the female coupler and, then, the sleeve is moved to the locking position.