A watertight electric connector has a male connector housing, a female connector housing to be mated with the male connector housing, a ring-shaped packing in close contact with an outer wall of the male connector housing, and a slidable protection cover disposed so as to cover the periphery of the packing. The protection cover protects the packing when the connector housings are not mated with each other, and is moved backward by the pressure of the female connector housing when the connector housings are mated. The slidable protection cover has a mechanism capable of making the watertight connector compact, simplifying the handling of the connector, assuring protection of the packing, and enhancing reliability of waterproofing.