Disclosed is a fuel leakage preventing valve, involving no variations in valve closing characteristics, in which a vertically movable float valve is arranged in a chamber defined inside a housing and in which a valve seat of the housing communicating with an outside is opened and closed by the float valve, which has a protruding step portion formed upwardly at the center of an upper surface of the float valve, a retainer fixed to the upper surface side of the float valve, the retainer having a flange portion covering the upper surface of the float valve and a cage portion raised from the flange portion to define an accommodating space in conjunction with the protruding step portion of the float valve; and a valve body for opening and closing the valve seat of the housing is rockably accommodated in the accommodating space defined by the cage portion.