To provide a connecting structure of a lure connector which can prevent germs from multiplying and a liquid chemical from being wastefully consumed, and to provide a male side connector used for that.

The male side connector 22 is composed of a male side connector body 26 made up of a base end connecting portion 31 connected to a tube 15 and a tip supporting portion 32 extending forward from the base end connecting portion 31, a male lure member 27 slidably provided in the interior of the tip supporting portion 32 with the tip side portion 27a projected from the tip of the tip supporting portion 32 and an elastic sealing member 29 installed in the male side connector body 26. The expansion hole portion 29a of the elastic sealing member 29 can be opened by the pressing force of the male lure member 27 by forming the inside periphery of the female side connector 21 into a tapered surface which can liquid tightly contact the outside periphery of the male luer member 27 and putting and engaging the male lure member 27 into the female side connector 21.