A light source unit of the present invention includes a luminescent material plate, a joining plate on one side of which the luminescent material plate is disposed, a heat dissipating member disposed on the other side of the joining plate, and a heat conductive layer configured to thermally connect the joining plate and the heat dissipating member together and disposed between the joining plate and the heat dissipating member, and a heat conductivity of an area of the heat conductive layer which corresponds to the luminescent material plate is lower than a heat conductivity of a periphery of the area of the heat conductive layer which corresponds to the luminescent material plate.