A connector, comprising: a housing forming a passage for conveying fluid from one end to the other end thereof, and connecting a first member on a side of the one end with a second member on a side of the other end; and a pulsation reducing member provided on the housing; the pulsating reducing member comprising: a cylinder formed in a hollow cylindrical shape integrally with the housing, having an opening portion on one end side of the hollow cylindrical shape communicating with the passage, and having an annular flange portion projecting in a radially inner direction of the hollow cylindrical shape; a piston disposed in the cylinder on a side of the flange portion opposite to the passage and movable in the cylinder; an urging body disposed in the region on the side of the piston opposite to the passage in the cylinder and applying urging force to move the piston towards the passage; and an elastic sealing member, formed in an annular shape, that restricts a fluid transfer in the cylinder between the region on the side of the piston near the passage and the region on the side of the piston opposite to the passage; wherein the urging body compresses the elastic sealing member; characterised in that the elastic sealing member is sandwiched in a compressed state between an end surface of the flange portion and an end surface of the piston, dividing a region on a side of the piston near the passage from a region on a side of the piston opposite to the passage in the cylinder, and changing the amount of compression in accordance with the position of the piston; wherein the elastic sealing member is formed of a material and shape which enables elastic deformation at least in an amount corresponding to a travel distance of the piston; and wherein the elastic sealing member always contacts the end surface of the flange portion and the end surface of the piston without separating from the flange portion and the piston, whichever position the piston is located in the cylinder. a housing forming a passage for conveying fluid from one end to the other end thereof, and connecting a first member on a side of the one end with a second member on a side of the other end; and a pulsation reducing member provided on the housing; the pulsating reducing member comprising: a cylinder formed in a hollow cylindrical shape integrally with the housing, having an opening portion on one end side of the hollow cylindrical shape communicating with the passage, and having an annular flange portion projecting in a radially inner direction of the hollow cylindrical shape; a piston disposed in the cylinder on a side of the flange portion opposite to the passage and movable in the cylinder; an urging body disposed in the region on the side of the piston opposite to the passage in the cylinder and applying urging force to move the piston towards the passage; and an elastic sealing member, formed in an annular shape, that restricts a fluid transfer in the cylinder between the region on the side of the piston near the passage and the region on the side of the piston opposite to the passage; wherein the urging body compresses the elastic sealing member; characterised in that the elastic sealing member is sandwiched in a compressed state between an end surface of the flange portion and an end surface of the piston, dividing a region on a side of the piston near the passage from a region on a side of the piston opposite to the passage in the cylinder, and changing the amount of compression in accordance with the position of the piston; wherein the elastic sealing member is formed of a material and shape which enables elastic deformation at least in an amount corresponding to a travel distance of the piston; and wherein the elastic sealing member always contacts the end surface of the flange portion and the end surface of the piston without separating from the flange portion and the piston, whichever position the piston is located in the cylinder. a cylinder formed in a hollow cylindrical shape integrally with the housing, having an opening portion on one end side of the hollow cylindrical shape communicating with the passage, and having an annular flange portion projecting in a radially inner direction of the hollow cylindrical shape; a piston disposed in the cylinder on a side of the flange portion opposite to the passage and movable in the cylinder; an urging body disposed in the region on the side of the piston opposite to the passage in the cylinder and applying urging force to move the piston towards the passage; and an elastic sealing member, formed in an annular shape, that restricts a fluid transfer in the cylinder between the region on the side of the piston near the passage and the region on the side of the piston opposite to the passage; wherein the urging body compresses the elastic sealing member; characterised in that the elastic sealing member is sandwiched in a compressed state between an end surface of the flange portion and an end surface of the piston, dividing a region on a side of the piston near the passage from a region on a side of the piston opposite to the passage in the cylinder, and changing the amount of compression in accordance with the position of the piston; wherein the elastic sealing member is formed of a material and shape which enables elastic deformation at least in an amount corresponding to a travel distance of the piston; and wherein the elastic sealing member always contacts the end surface of the flange portion and the end surface of the piston without separating from the flange portion and the piston, whichever position the piston is located in the cylinder.