A driving source assembly includes: a prime mover including a driving shaft; a continuously variable transmission including a CVT case; a first gear that is between the prime mover and the CVT case and rotates together with the driving shaft; a second gear that is meshable with the first gear; an energy converter including a rotating shaft that rotates in association with the second gear; and a plate which is fixed to the prime mover and to which the energy converter is fixed. The first gear is between the plate and the CVT case. The CVT case includes a recess that defines an auxiliary accommodating space accommodating the first gear. The seal is between the recess and the plate.