A hybrid driving force transmission device includes a motor generator (9), a multi-plate dry clutch (7), a housing cover (60), a dust seal member (62), and a dust collection structure (63). The multi-plate dry clutch (7) is disposed at a position inner than the motor generator (9). The housing cover (60) is provided to cover the motor generator (9) and the multi-plate dry clutch (7), and divides the internal space into a clutch chamber (64) and a motor chamber (65). The dust seal member (62) is disposed at a position radially outside of a clutch chamber open surface (66) and seals between a rotor (92) and an inner wall (60a) of the housing cover (60). The dust collection structure (63) forms a dust collection space (69) in a region radially between the seal surface (68) formed by the dust seal member (62) and the clutch chamber open surface (66).