A driving force transmission device includes a clutch housing configured to be connected to a propeller shaft; a shaft including a weakened portion that is a portion in an axial direction of the shaft; a multi-plate clutch disposed between the clutch housing and the shaft; a case member including a housing portion having a cylindrical shape, the housing portion being configured to house at least a part of the clutch housing; and a falling-off preventing member configured to, when the shaft is broken at the weakened portion, allow rotation of the clutch housing while restraining the clutch housing from falling off the housing portion.