An inner peripheral surface of a tube connecting portion of a tubular connector housing is divided into a first receiving portion on one axial side and a second receiving portion on an opposite axial side by an inwardly directed annular parting projection. A first O-ring of one axial side and a second O-ring of an opposite axial side are disposed with intervening a collar therebetween on an opposite axial side in the first receiving portion. The first O-ring is made of FKM and the second O-ring is made of FVMQ. A third O-ring is disposed on one axial side in the second receiving portion. The third O-ring is also made of FVMQ.