A filler device comprising: a filler neck including a pouring inlet through which a fuel is injected and a neck connection portion; a connection pipe including a pipe connection end to which the neck connection portion is connected and a bellows part which is curved along a filling passage to a fuel tank; wherein the fuel injected through the pouring inlet is fed into the fuel tank through a filling passage, the connection pipe is provided with a pipe-side engaging portion on a back side of the pipe connection portion, the filler device further includes an inner tube including a tube body formed of a flexible elastomer material and inserted into the connection pipe, and a tube-side engaging portion projecting from an outer circumference at an end of the tube body, the inner tube is configured so that the tube body covers an inner wall of the bellows part and that the tube-side engaging portion is engaged with the pipe-side engaging portion, when the inner tube is inserted into the connection pipe, reaching to the back side of the pipe connection end.