The utility model provides a liner maintenance structure which is capable of preventing a liner located at a front end cylindrical part from detaching even in the case of repeated plugging and unplugging of a charging connector to and from the front end cylindrical part of an inlet shell in a secondary battery side connector. The liner (7) comprises a cylindrical basic cylinder part (71) and a sealing ring part (72) formed in a manner of protruding from the center in the axial direction at the inner periphery of the basic cylinder part (71). The front end cylindrical part (52) of the inlet shell (5) comprises a groove forming wall (61) which forms an annular cylinder part embedment groove (63), wherein the basic cylinder part (71) of the front end side of the liner (7) is embedded in the cylinder part embedment groove (63); and a front holding rack (62) which has a cylinder part pressing wall (621) extending over the basic cylinder part (71), embedded in the cylinder part embedment groove (63), of the rear end side of the liner (7). The groove forming wall (61) and the cylinder part pressing wall (621) clamp and hold the sealing ring part (72) in the axial direction.