Connection tube for fuel tank

A connection tube for a fuel tank having an opening, comprising:

• a joint part including a weldable part weldable on the fuel tank at the opening and a connection tube part including an inner circumferential face;
• and
• an inner tube, fitted in the inner circumferential face, and contacting the inner circumferential face, the connection tube part and the inner tube comprising materials having different swelling rates against a fuel to be stored in the tank, wherein one end of the connection tube part and one end of the inner tube include slopes therearound in contact with each other, respectively, the slopes being inclined from the axial direction of the connection tube part and the inner tube, wherein when the connection tube part and the inner tube swell due to wet with the fuel, the slopes have relative displacement in the axial direction and a radial direction of the connection tube part and the inner tube with contact therebetween.