1. A semiconductor element cooling structure for cooling a semiconductor element, comprising:
a heat receiving unit configured to receive heat emitted from the semiconductor element; and
a heat radiation unit configured to radiate the heat from the heat receiving unit,
wherein:
the heat receiving unit includes an element contact portion having a contact surface to which one surface of the semiconductor
element is fitted, and a heat diffusion portion that is contacted with the element contact portion and the heat radiation
unit;

the element contact portion includes a space portion;
the contact surface includes a through-hole which communicates with the space portion and through which a terminal of the
semiconductor element is inserted;

the space portion houses a substrate to which the terminal of the semiconductor element is connected; and
a thickness of the heat diffusion portion in a direction from the space portion to the heat radiation unit is in a range of
3 mm to 8 mm,

wherein the heat diffusion portion is disposed between the space portion and the heat radiation unit.